First of all, many thanks to Radix and Mike Uyama for keeping SDA up and 'running'! It's an absolutely amazing community and I'm happy I finally decided to sign up, after watching many of the submitted videos for a few years.
I would also like to express my gratitude to Mike "mike89" McKenzie, for providing me with some useful tips and trivia for the run, and to Zeupar, whose recent interest in my run provided me with more motivation to actually getting it recorded and submitting it.

The first time the idea of speed running the game crossed my mind was when I had about 30 minutes left until the start of a lecture, and I had nothing to do. I decided to see whether I could clear the game in time (100%), and to my surprise I succeeded. A few months later, after watching a few SDA runs, I figured that I should try and come up with my own video for this wonderful website. I started working on a proper speed run some time in February 2011. With several months of very little playing in between, it has taken me almost precisely a year to finally get the run recorded.
Anyway, I've added some commentary below for each individual level. I might throw a video of all the ridiculous glitches in the game along with some bloopers on YouTube later on, should anyone be interested. Hope you enjoy the run!

Intro cut scene
How to entertain oneself:
Mash all your buttons to make Sonic jump during the cut scene. He's actually supposed to do a peel-out, but if you mash accurately enough, you'll be able to make him jump instead, ruining the entire cut scene.

Character selection
Things that can go wrong:
*You could accidentally select Tails instead of Sonic when trying to do a Sonic speed run. Yes, funnily enough, that has actually happened to me once, forcing me to reset.

Turquoise Hill Zone 1
Most common ways to make you reset:
*Jumping instead of peel-outing while the screen fades in. This happens all the time, and makes you lose a second. Since it's the first level, that's not really acceptable.
*Missing the spring around the 0:02 mark. You'd be amazed how often this has happened to me. I've even managed to land in front of it a few dozen times. No idea how I managed to pull that off.
*Not running far enough up the hill around 0:04. This will make Sonic do some kind of moonwalk, which means you won't be able to do a peel-out.
**Alternatively, you could break too hard, making Sonic face the wrong way. A peel-out will then make you go back to the beginning of the stage.
*By far the most common cause for a reset was that I ran straight into the enemy at 0:05. The jump I have to do there has an incredibly tiny time window, and I tend to miss it very often.
*Missing the spring-enemy at 0:06.
*Not roll-jumping right after you land

Not only did I not make any of the above mistakes, but I also reached my personal best time of 0:10! Out of the well over a thousand attempts at running through this level, I only managed to get 0:10 about 6 or 7 times, hence this was a very pleasant surprise. Overall, this is the level that made me reset the most.

Turquoise Hill Zone 2
How to mess up and reset:
*Jumping instead of doing a spin-dash at the start. There's no audio or visual cue you can use for the start of this level. If I wasn't spin-dashing before the screen faded in, I had to reset.
*Rolling too far/not jumping high enough on the ramp around the spring-enemy.
*Hitting the invincibility box on top of the loop. The amount of lag this causes is incredible.
*Accidentally getting launched by a hidden underground spring around 0:06.
*Rolling into, but not breaking the rocket-shoes TV.
*Getting hit by the flying enemy around 0:10.

I again managed to avoid these reset-worthy mistakes, and go through the level in a very neat 0:11. There's an alternative route that is a fraction of a second quicker, but it would've increased my number of resets fivefold and was definitely not worth the hassle. It involves skipping the rocket shoes and doing roll-jumps on and off the third pillar near the end. I've pulled this off a couple of times, but it's honestly really not worth the trouble.

Turquoise Hill Zone 3
Reasons for a reset:
*Not doing a peel-out at the start. A very interesting fact about the majority of the levels in this game is that Sonic isn't standing on the ground when he spawns. Instead, he's floating a tiny bit above the ground. Pushing the buttons to do a peel-out (up+jump) would then result in Sonic doing a jump, instead of dashing, resulting in a one-second loss.
*Missing the spring. I used to miss it all the time, until I finally came up with a visual cue for jumping. Finding the visual cue made it a reset-worthy mistake for me.
*Hitting wall right after the spring-jump. It forces you to land in front of the spikes and do a peel-out jump, which results in a loss of a bit more than half a second.
*Landing on top of the spikes, rather than right behind them, resulting in instant death.
*Hitting the boss' spring, launching you upwards.
*Not doing the dashes quickly enough (this usually happens when the boss is a bit too far away from the side).
*Dashing too quickly, resulting in Sonic clipping through the boss. That's right, you can both dash too slowly and too quickly for this boss. Fuck my life.
*Peel-outing too early once the boss is dead, making you hit the invisible wall. It costs about half a second if you hit the edge before the screen starts scrolling. Ideally, Sonic's nose should be touching the edge of the screen as he runs to the right while the victory tune is playing, but this is something only a TAS could do perfectly every time.

Everything went quite according to plan in this level. The boss fight is a complete joke when you use this spin-dashing method.

Gigalopolis 1
List of things that can ruin your day:
*Trying to do the peel-out too early at the start. This is another one of those levels where you can clearly notice how Sonic is floating above the ground at the start, making it somewhat tricky to do the peel-out.
*Jumping too low near the ring-boxes, making you enter the tube. Not only do you lose a fraction of a time by having to respond to this unfortunate event, but due to having to break, it's a tiny bit slower.
*Jumping too high near the ring-boxes, making you bounce off the enemy. Doesn't cost as much time as jumping too low, but it's still a tiny bit sub-optimal.
*Missing the platform floating over the spikes, making you land in the spikes. It doesn't result in an instant death, but still wastes well over a second as Sonic has to recover.
*Failing to roll-jump off that platform as soon as you land, again result in hitting the spikes. Hitting the spikes in either of the two possible ways definitely means one should reset.
*Not hitting the roof after the spring jump. Hitting the roof reduces Sonic's air time, allowing you to continue with the level more quickly. Not really reset-worthy, but it's really easy to get it right anyway.
*Failing to do a peel-out-jump while on the small platform, making you fall down.
*Jumping too early near the horizontal spring. It makes Sonic land awkwardly in the next part and forces the player to walk back a small distance, to do the final peel-out.

Unfortunately, I fell prey to the third mistake and bounce off the flying enemy. It's the smallest mistake I could've made in the level, and I still end up getting 0:16 (albeit a late one) on it because everything else went perfectly, so I decided to go with it

Gigalopolis 2
How to mess up:
*Not waiting for Sonic to touch the ground at the start. He starts off floating in the air again, so I have to start my peel-out a bit later than I would've liked to.
*Killing the enemy around 0:11. This happens if you do the preceding jump too early. Doesn't cost much time, but it's certainly annoying when it happens.

The run through this level went quite well. I think there's an alternative way of clearing it that is a tiny bit quicker, but for the sake of consistency I decided to go with the route that I pretty much always get right. Given the previous level's time, I expected to get a mid 0:14, but I somehow got an early one instead.

Gigalopolis 3
How this level can make me unhappy:
*Not rolling far enough to grab the invincibility box on top of the loop. I really need this one for the boss strat I use, and not getting it makes me lose a bit of time during the coming fight.
*Jumping too early before the boss appears, which results in Sonic being launched away without dealing any damage. Doesn't happen very often, but it's incredibly annoying when it does.
*The boss ignoring Sonic's attacks. Ohh, I truly hate this glitch. Quite often, I hit the boss straight on the head, but he doesn't take any damage. I've even had this happen twice in a row during a really good run, which made me lose at least 2 seconds. It doesn't make any sense, but is extremely frustrating.
*As in THZ3, peel-outing too early after the boss' death. Happens all the time, as there are no clear visual or audio cues.

All in all, the level went very well. I miraculously avoided the above mistakes. In particular, the boss-invincibility glitch happens to me nearly every run, so I was quite pleased that it didn't occur this time. There's also a useful glitch in this level, but it's only happened to me twice so far. It involves Sonic clipping through the boss' head on the 4th hit, so that you land on the other side. This allows you to hit his head very quickly again, resulting in the boss' swift defeat.

Sleeping Egg 1
Reasons that make me throw away my controller:
*Jumping too early at the start, making you land on top of the spring and hitting the wall. It looks hilarious, but unfortunately wastes more than a second.
*Jumping too late at the start, and being launched away by a hidden underground spring. This causes a stupid amount of lag, as Sonic breaks through the above blocks, that it definitely qualifies as a reason to reset immediately.
*Jumping too late at 0:06, making you fly over the rocket-shoes box, resulting in instant-death.
*Bumping into anything while flying on the rocket shoes. It's really annoying to steer Sonic while he's flying, so it took me quite some time to learn how to avoid all the walls.

Very happy with how this level turned out. I time everything pretty much perfectly. Only end up breaking a single block at the very end, but that doesn't really matter.

Sleeping Egg 2
Why this level haunts me in my dreams:
*Missing the first spring.
*Missing the second spring. Getting the first one is trickier than this one, but it's still incredibly easy to miss this one as well.
*Jumping off the second spring too early, making you break the TV box, but not land where this box stood. This wastes about three seconds, as you have to jump back to the first spring to get to the top. Definitely reset-worthy.
*Bouncing off the ring-TV box at the top. Doesn't cost much time, but it's still unfortunate when this happens.
*Breaking too early near the curved ramp, making you miss the platform and the TV boxes.
*Breaking too late near the curved ramp, making you fly up way too high.

Everything went really well. I very often miss one of the two springs, or bounce off the TV box so I was very happy to see that I avoided those traps. I could've braked a tiny bit earlier on the curved ramp, but I still got it nearly perfectly.

Bonus Stage 1:
What could possibly go wrong here?
*Accidentally breaking the TV and grabbing the rocket shoes. Yes, that actually happened to me once.

This level probably needs some additional clarification. In order to get the 'good' ending for the game, Sonic has to collect 5 Chaos Emeralds. These are hidden across 5 special Bonus Stages and the only way to reach such a bonus stage is to collect 100 rings, which instantly teleports you to a specific bonus level, while skipping the rest of the regular level. Rather than actually completing this bonus stage (which would take ~30 seconds, I guess) I simply fall off and die as quickly as possible. This ends the stage and makes me go straight to the score screen. You might think that doing such a bonus stage is a waste of time, since I'm clearing two stages rather than just one, but I can assure you that it's not. I not only skip about 4 seconds worth of Sleeping Egg 2, but I also don't have to wait for the sign to fly up and land at the end, for the km/h score to appear, and for the final score screen (as I obtain zero points for failing the incredibly trivial bonus stage). Overall, this is a gigantic time save, regardless of which timing method is used, and is truly a must for the speed run. As a sidenote, it doesn't matter which side of the TV box I walk off. I couldn't detect any time difference, so I simply decided to "Hold Right to Win".

Sleeping Egg 3
Possible mistakes:
*Hitting to boss at an awkward angle. If you're a tiny bit too far to the left, Sonic will be launched away and the entire boss fight will be ruined.
*Dashing too early after the boss is defeated. As always, this is a minor mistake - especially compared to the one above.

I was a split second too early with the peel-out at the end, so unfortunately I still hit the edge of the screen right as it started scrolling. Oh well - it's still significantly better than being too late with the peel-out. Everything else went really well.

Mecha Hill Zone 1
Why this level can be unpleasant:
*Being screwed over by the whole Sonic-Spawns-In-The-Air nonsense at the very strat of the level. You have to wait a fraction of a second to make sure he's actually on the ground before dashing.
*Jumping a bit too late or early at the start, making you miss the rocket-shoes box.
*Flying a pixel too high, making you hit the coconut-grenades. My old route actually involved getting hit by these, but I soon found out that dodging them is slightly quicker.
*Flying too low, making he hit the spring, which doesn't launch you far enough to skip the bridge. Instead you fall off the bridge, and have to get back up using a spring. This is a huge time waste.

Nothing remarkable here. Everything goes according to plan, and I clear the level as quickly as ever. Apart from the bonus stage, this is probably the easiest level to run through.

Mecha Hill Zone 2
How this level can make me miserable:
*Missing the spring by jumping over it. I don't think I've ever landed in front of it, but I've flown over it several times. It generally doesn't result in instant-death, but it's enough to make me reset the run.
*Going too fast on the bridge. You have to slow down a bit while in the air. Otherwise, you end up either the wall while jumping onto the ramp, or you could overshoot your landing zone, forcing you to walk back a bit before the following dash-jump
*Going too slowly on the bridge. This will simply make you fall through it, forcing you to use a spring to get back up. This is a rather big waste of time.
*Hitting the horizontal spring when doing the dash-jump. This launches Sonic quite far back, and makes the player lose at least a second.
*Missing the spring after the dash-jump. It's actually a rather small time waste if you miss the spring, but it makes the level a hundred times more difficult to clear from this point onward.
*Not hitting the 1Up box after jumping off the spring mid-air. If you overshoot it, then you end up losing a bit of speed and if you land in front of it, Sonic comes to a halt. Either way, it's better to hit the box.

Absolutely perfect! Couldn't really have wished for a better run through this level. Every jump and dash goes exactly as planned and I avoid all of the above, common mistakes.

Mecha Hill Zone 3
Possible unfortunate events:
*Peel-outing too early at the start. Yes, this is yet another case where Sonic starts off mid-air rather than on the ground.
*Jumping too early before the bridge, making you not-reach the other side in one go. If you're unlucky, this will even make you fall through the bridge, resulting in a huge time loss.
*Killing the boss in 5/4/2 (or 4/5/2) hits, rather than 5/5/1. Getting 5/5/1 is incredibly hard, but failing to get it leads to a very small time loss.
*Getting crushed by the boss by standing underneath him. You'll be pleased to hear that I once had to reset a good run, because I somehow clipped through the boss and landed underneath him.
*Falling into the spikes. This is especially painful if you've already defeated the boss and are waiting for the screen to scroll to the right.

Sadly, I didn't get the 5/5/1 kill on the boss this time, and had to settle for 5/4/2. My first 5 hits were timed perfectly, and I *could've* gotten 5/5/1 here, but the jump after I landed was a few pixels too high. From the looks of it, I missed 5/5/1 by possibly as little as 1 or 2 frames. Still, everything else went fine, and 5/4/2 is still acceptable at this point of the run.

Aqua Planet Zone 1
Causes for depression:
*Get screwed over somehow by the ridiculous amounts of lag in this level. Seriously, Sonic is uncontrollable half of the time. It's like the console thinks you're controlling the game with a chikin sammich (which is, by the way, the correct way of referring to a piece of chicken in a bun).
*Jump too late after the initial peel-out, making you hit the wall. It actually doesn't cost that much time, though it forces you to do a spin dash rather than a peel-out upon landing on the platform (otherwise you'll die to the jolly-jumpers (-this is probably not their real name))
*Lose control over Sonic while running/rolling. Yep, that's right. Sometimes you can't control Sonic any more, and he'll just keep on going right, until he gets hit or falls off an edge. When he falls off, he'll drop incredibly quickly and you'll regain control again once he reaches a full stop. By that time, this glitch will have already wasted countless precious seconds.
*Bounce off the second jolly-jumper triplet, making you miss a few rings.
*Clip through the breaking platforms, making you fall into the water. Oh, I should mention that water causes an *extra* ridiculous amount of lag, so if you actually end up there you'll probably lose at least 15-20 seconds.
*Hit the spikes after jumping off the second breaking platform.
*Sonic getting stopped instantly by one of the Ring-TV boxes, rather than just rolling through them. This is another fun thing the game sometimes randomly pulls out of its hat.
*Having 59 instead of 60+ rings after collecting the first 3 Ring-TV boxes. Very minor mistake, but it forces you to jump into lag-hell at the end of the stage to collect the last ring.
*Missing the jump onto the peel-out jump onto the loop.
*Hitting the boxes on top of the loop awkwardly, making Sonic either stop dead in place, or bounce off randomly.
*Did I mention the lag in this level?

Despite all the ridiculous problems with this level, I manage to get through it perfectly. The time I set here comes very close to my personal best, and is a lot better than what I expected to get here. Definitely happy with the result. I even nearly got 0:13 on the timer.
Those with suicidal tendencies are strongly recommended to avoid this stage at all cost, as it will drive anyone except masochists insane.

Bonus Stage 1
You can still screw up by:
*Getting the rocket shoes, somehow.

Since I failed this bonus stage the first time, I get the opportunity to re-do it. Instead of clearing it, I follow the same strategy as above and simply fall off as quickly as possible. Collecting 100 rings and clearing the bonus stage is ridiculously quick and consistent compared to doing Aqua Planet 1 the regular way. By skipping a portion of the level, I get to skip a lot of Aqua Planet's awful lag.

Aqua Planet Zone 2
As if the first Aqua Planet wasn't horrible enough:
*Missing the spring after the initial dash-jump or peel-out jump. Actually hitting the spring is very difficult, and my success rate is rather low for it. Missing it costs less than a second anyway.
*Hitting the spring after the initial jump, but you're going too quickly. This will result in Sonic being stabbed to death by the moving spike right next to the spring.
*Not hitting the ceiling after the spring jump. Only happened to me once, as it's very easy to hit the ceiling. Missing it is a pretty big waste of time, though.
*Missing the peel-out jump, resulting in hitting the boxes awkwardly. Sonic will either come to a dead stop, or bounce off a box, making him get launched away. You need all the boxes here to reach the bonus stage quickly.
*Somehow screwing up the roll-jumps on the horizontal bits, making you fall off at the end, and/or missing the final jump toward the last couple of boxes.
*Bouncing off the last set of boxes.

As I had already pretty much expected, I failed to land on the first spring. I rarely get it right, even after lots of practice, so this isn't really a big issue. I guess it's reset-worthy in IL attempts, but definitely not this far into a really good full run. Other than that, all my jumps are timed precisely as planned and I clear the level in a neat and swift fashion.

Aqua Planet Zone 3
How this simple boss level can end up being quite annoying:
*Sonic starts off mid-air again in this level, so you have to be careful with the first peel-out.
*Missing the first jump that skips the first few springs.
*Somehow fall through the breaking blocks, rather than going through the secret path at the top.
*Actually thinking the invincibility box at the top is useful. It really isn't.
*Getting crushed by the boss when he lands on top of you.
*Getting launched away randomly while attacking the boss.
*Failing to use the wall-bouncing glitch at the correct time. This happens quite a lot, because it's a rather messy glitch.
*Getting hit by the bullets the boss shoots
*Getting hit by one of the rockets the boss shoots. This generally doesn't cost any significant amount of time, but it's still better to avoid them.

Everything goes very well in this level. Notice how my first hit on the boss somehow doesn't register. This doesn't actually end up making any noticeable difference, since the wall-glitch allows me to hit him very rapidly. I used to get hit by the middle rocket from the left on purpose, but I decided to do it a bit more fancy by dodging all the rockets this time.

Electric Egg Zone 1
I hate this level because:
*Somehow getting hit by the first laser. Hardly ever happens, but it's infuriating when it does.
*Missing the Jump-Of-Faith around 0:12. I really hate this jump, because it's difficult to get, and forces you to reset if you miss it (since missing it means that Sonic dies).
*Going up, instead of to the right, right after you enter the tube.
*Bouncing back to the left instead of going up in the latter portion of the tube.

This level design is awful for speed running, but I manage to get through it pretty much perfectly. I could've done a second roll jump in between the two exploding enemies, but this is rather risky and makes me miss the Jump-Of-Faith quite often, so I decided to go for the more consistent method. It went so well that I nearly got a time of 0:15. Just barely missed it.

Electric Egg Zone 2
A possible series of Unfortunate Events:
*Getting screwed over by the ridiculous amounts of lag. It's Aqua Planet all over again.
*Being sucked into the tube rather than going just past it. This wastes about 3 seconds
*Getting hit by a laser
*Hitting an exploding enemy
*Not doing the peel-outs quickly enough to avoid the exploding enemies' shrapnel.

Electric Egg 2 has broken quite a lot of my more successful runs. The lag on top of the breaking-bridge makes jump timing and the peel-outs a lot more difficult than they should be. I was very happy to get past the entire stage without any errors. It went so well that I even nearly had a late 0:16 at the end!

Final Egg Zone
Why I considered alcoholism as my profession:
*Missing the final platform when falling out of the tube. As awful as it may sound, this trivial mistake would lead to a reset for the entire run. It costs 3-4 seconds, because you have to take a slow lift back up. It's not a terribly difficult trick, but I've missed it at the end of my runs numerous times. Being nervous at this point certainly isn't helpful.
*Making Robotnik launch a bouncing bullet by staying too far on the right while bouncing on top of him. These buggers are very hard to dodge - especially while bouncing on top of our fat moustached friend.
*Getting hit by one of Robotnik's bouncing bullets. Not only throws you out of the bouncing rhythm, but causes a nasty loss of almost 2 seconds.
*Bouncing too far on the left, resulting in Sonic being launched away across the screen. Why does Sonic get launched away by this? Because Sonic physics; that's why!
*Dashing too early to the right once the first phase is over.
*Getting hit during Robotnik's second phase, resulting in instant death.
*Not getting the floating-Robotnik glitch at the end. It looks hilarious how the game thinks he's standing on top of the floating platform even though he's not even close to it.

I was really happy to have reached the platform when falling out of the tube. Somehow, I mistimed my first bounce on top of Robotnik, which made him launch a bouncing bullet. I skillfully dodged it, and finished him off very nicely. Ideally, one should keep him to the right of the screen, so that he leaves it very quickly, but I didn't want to risk losing this great run for the small gain this would bring me. In the second phase I jumped a tiny bit too early, making me hit Robotnik a bit further to the left than I had wanted, but fortunately, this didn't cost me much time. I manage to get the floating-Robotnik glitch, by dashing at the precise right time.

Overall, I'm extremely pleased with the run. After way more than a thousand resets, I've finally completed the game in a satisfactory way. Overall, using some new strategies I have in mind, I see the potential room for about 4-5 seconds worth of improvement (including the tiny mistakes I made throughout this run), most of which is practically impossible in a full run, due to the ever-present lag, the often unresponsive controls, and the random annoying glitches the game tends to throw at the runner.
I might consider working on a 100% run (as that would only require minor modifications to the any% route), but I'd much rather focus some attention on my other speed running projects.