I was mainly talking in my first post about his spin charge, in fact, and not about his general speed. Sorry if it was unclear (notably because of the title I guess). And the fact that this attack cannot eject other character (while it is one of his attack that caracterize him the most).
About what you two are saying, \Apples and SilentDoom, do you think it is important for Sonic (as Sonic himself, not Sonic in SSBPM) to move easily in the air? As I was saying upper, I think his speed could be so usable mostly on the ground (he is a runner, not defying physic laws everytime his body moves wherever he is). All I am humbly proposing here, as a player that likes the character but not what he is in SSBPM, is to rethink the character's gameplay. His present gameplay force players to make combo to kill other player, don't you think it is a bad thing?
One of the problem in his gameplay is his lack of ejecting attacks, that is why I am supposing a gameplay for him where he does not move so fast in the air, and therefore would be more powerful in the ground than now (and then his spin charge would eject). Do you think such a gameplay could be interesting, and doable? (Considering that you know better than me the game mecanics.)
Well, his spin charge is plenty fast. Speed is relative to reaction time. Now, I'm not sure exactly how fast he is with his Down+B uncharged, but it's pretty fast. Fast enough that for most characters, he can start an uncharged Down+B just outside their threat range (I'm just using this term, threat range, to refer to the relative space around a character at any given time during the neutral game where entering this space becomes dangerous. for instance, for Marth, this distance is his current location + the furthest reach of his dash attack in your direction. Same with Sheik and Peach. For Fox, it's SH Nair, for Ike, it's uncharged Side+B + RAR Bair or Fair. For Falcon, it's SH Nair.) So for Sonic, his threat range is pretty enormous considering his crazy good dash and run speed. His air speed is what makes him threatening. This threat range is made less severe when projectiles enter the equation. Sonic's Down+B locks him to being on the ground, as does his incredible run speed. Being able to jump and change your position in vertical space is so integral to this game's fundamental combat system that if Sonic were not able to carry his momentum from his running into the air, he'd practically be useless because his ground options are all very slow. A great way to overcome this is to hop over projectiles, and aerial Down+B as you're passing over the projectile, leaving an opening for Sonic to zip straight to his opponent and hopefully pop them up into the air and open a can.
Anyway, if his Down+B is any faster, it'll just become too difficult for the human brain to react to. There needs to be a healthy balance of moves that must be read vs moves that are telegraphed. If a move must be read, it shouldn't be spammable i.e. it should have a major downside. Honestly, I think Sonic is perfectly fine as he is, though if anything, I think his uncharged Down+B could stand to be just a tad slower, while maintaining his current max charge speed. The ridiculous max charge speed is counter-balanced by having to charge for so long, which gives your opponent more time to react/prepare for the approach. This is the reason PMBR removed Sonic's ability to jump cancel and thus wavedash out of Down+B because he didn't have to commit. The move was broken because Sonic's threat range was insane. The entire stage was unsafe, even though the move did barely any damage, it would still set up combos and could even pressure shields. **** was whack, yo.
Consider what a character focused solely on incredible ground mobility requires to operate effectively. Let's look at Luigi for an example. His dash and run speed are atrocious. However, his wavedash is incredible and gives him excellent horizontal mobility if he has a ground surface to perform perfect wavedashes on. Yet he does not carry this speed with him into the air, he slows down when he jumps. In order for such a moveset to work, his ground options must be fast and be able to set-up and/or extend combos. Jab is great for him because he's relatively safe and can slide through shields with it. If it pokes, he can stop himself using his jump or wavedash back and grab or use another attack and take advantage of that little opening he created. Obviously, CC is a counter to this. Utilt is great for starting combos, great coverage on both sides, comes out fast and he can use it to intercept opponents trying to get to the ground after an aerial, squeeze in and use those opportunities as openings to punish. Same with Dsmash, similar tool with higher priority and more knockback, better on faster-falling characters, but can get kills at higher percents on floatier, lighter characters. Ftilt is a great, fast spacing option. Etc.
So, Sonic's moveset would have to be completely redesigned for something like this to actually work. We already know that Sonic is a jumper, though. He jumps in all of his games and uses his jumping abilities to extend his speed into vertical space, allowing him to reach higher goals. The trick to stringing Sonic's moves together well involves proper use of DI; slowing yourself down at the perfect time such that Sonic avoids being too early and getting hit, but avoids being too late and missing with his attack. Even more precise, is being just on time so that you still get your aerial through and it connects, but you also adjust your air speed appropriately so that you can follow up with your next aerial. Homing Attack is also an important tool for the mitigation of misestimating your air speed after connecting with an aerial and allows Sonic to correct his errors in air speed control.
Hope most of that makes sense. Cheers.
P.S. I'm not a Sonic main at all, but thinking about this makes me want to take him more seriously.