Sonic's actor is the biggest controversy. I honestly don't mind the new guy that much, it's just, like you said, SOMEBODY, PLEASE GET HIM SOME GOOD DIALOGUE!!
... no but really, I just don't like Smith's voice on classic Sonic (if I was hearing it right, and I'm sure I was). It just doesn't fit, especially since supposedly the reason they picked Smith was to make Sonic sound older, so using him to voice classic Sonic seems kinda contradictory. Unless it's to tease us...
Anywho, hopefully, since it's on the PS3/Xbox, the controls will be Unleashed-style, and let you use drift and quick-step all the time and not in stupid certain sections like in Colors. And I wonder if they'll tweak it so that the behind-the-back running portions don't have such sloppy and skiddy controls that force you to use quick-step in order to move properly; I liked Unleashed, but that was my one complaint. And that boost goes back to collecting rings; collecting white Wisps was stupid. Those are my only real hopes, and I'll probably be fine anyway if they don't come true, but that's just me.
Though I will say. These are the first teaser/gameplay vids in a while I've seen that didn't make me nervous. Well, I mean slightly nervous, but not in the way the others did. There was Sonic and the Secret Rings, wasn't sold on the Wiimote-tilting controls (and I was right). There was Sonic Unleashed's Werehog (which wasn't that bad in the end result). There was Sonic and the Black Knight, with the sword. And Sonic Colors... One word: Wisps. Level design in the game was okay. The Wisps ruined it. Too haphazard and gimmicky.
But so far, I've only had excitement from seeing Sonic Generations's teaser, with only minimal doubts. And now that I've seen the gameplay, most doubts have been erased; now to see if it'll actually be good. Classic Sonic gameplay combined with modern Sonic gameplay. Not so bad. Let's just cross our fingers for Classic Robotnik.