Continuing on the point of using specials, I haven't watched your vids again in a while, and can't quite watch them now(weird disconnects when i try to watch youtube vids), but just wanted to add some points.
-Homing attack is a great punisher against opponents charging smashes that have a hitbox which comes out mainly horizontally. It can also be very useful for an unexpected recovery every once in a while if say you are playing a gimp happy char like MK, are sent flying far away, and don't have your second jump available. Although spring is great, approaching from far and about stage height can let you be easily gimped. But a video is the best explanation, check this out at about 1 min:
http://www.youtube.com/watch?v=FV2tn5-ExiE
Had he not used HA, he would've been gimped and probably lost the round.
-Spincharge: People have serious misconceptions about the priority of this move. If not too stale, it will clang with tons of "high priority" ground moves at distances of about half the length of FD and less(at least when fully charged). Notice I said ground moves, because I think the interacton between aerials and an SDR is different. Jumping out of a spindash/spin charge roll however, into what we call a spin dash jump(SDJ) has very little priority, and is often where Sonic's get outprioritized.
-Spindash(Sideb): We covered it enough, but its incredibly versatile. Invincibility frames, setting up jab locks(SideB to footstool, spring, autocancelled dair, then jab lock), shield cancelling. Use invincibility frames on a fully charged aurasphere or Samus super ball beamy thing, it will frustrate your opponent to no end XD. It can be shieldcancelled anywwhere between input and a full charge. Once its fuly charged, you can't shield cancel it. Use SideB before your second jump for a huge gain on horizontal recovery. Not to mention that if you use it after your second jump, it will result in the infamous Sonic SideB suicide =P
-UpB, not much too say, lol. Invincible for about a full hops length after the spring is spawned, which is neato, and overall your best options for escaping combos. Don't get grabbed out of it though. To avoid this, you can "hug" the edge with a Uair as you rise, as its first horizontally disjointed enough to not let you be grabbed by most chars. Also, if you are ever too low to recover with just an UpB(rare, but it happens), and are near the edge in FD, you can just use upB on under the lip, then wall jump to grab the edge. Its awesome.
Umm lets see, about ROB. Like BlueTerrorist said, DownB actually isn't that good of a choice here because of Gyro. Dash attacking though, is XD. Use gyro against rob! lol. Dash attack stays out for a long time, so you easily grab robs gyro and glide toss it back at him. Also, Rob has a weakspot if you approach diagonally, which is why Aerial Spin Charge comes very much in handy here. Not to mention that rob is terribly easy to combo into with it, followed up by an aerial.
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? Your Sonic could be better and needs some work, but it's definitely not the worst. I look forward to seeing your Sonic in the future 
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