Terrible controls prevent me from even finishing the game.
What makes it even worse is that they tried to make Sonic move fast, but that failed because they forgot to give him weight to go along with it, now the slightest thing runs into him and he goes flying into oblivion in the most annoying way possible. That wouldn't be a problem if they didn't have sequences where he's running so fast the only thing you control was his direction. On top of that they switch the camera the opposite direction to show you where you're going. And then of course... you die.
What do I dislike the most?
Aside from the fact that Elise's whole character bothers me, I would say, loading times and environment.
Since I haven't had too many camera issues other than the camera switching behind you and throwing you completely off, the loading times are crippling. If you want to talk to someone because you have to to get through the game, You must go through a series of very pointless cut scenes that take longer to load than the cut scene takes to finish. And another to exit the cut scene. Sonic Adventure didn't even have this issue. Makes me wonder what happened.
Now to the environment. Levels are well designed, but are annoying because it doesn't finish rendering until you've fallen into a hole, run off a cliff or an enemy pops up underneath you and you die. I'm not sure if anyone else had this issue, but I did various times. One incident was in Crisis Core and there's a cliff and a bouncer. Sonic for some reason unable to slow down, hits it only to find there is nothing for you to land on or attack to keep from dying. As you're falling into the lava, you see fire birds start to load and a rail to get to the next part of the level. Now I'm not sure why they are unable to render games properly and I really don't want to know, but shouldn't the level already have rendered by the time you start? Then they have loading screens in the middle of a level. I'm not sure if they had no other way to make a more practical transition. Maybe one that lasted less than 2 seconds would be nice. It's like they're loading the whole level all over again and it still hasn't even finished rendering by the time you get past it.
I really thought the game looked nice, but I had read the original review before hand and decided not to get it. My sister had wanted to give it a chance so she bought it anyway. I think she's sorry she did because she quit long before me. Kind of feel sorry for her. It did look really good, and the story has a lot of potential. Good music, great CG's... If it weren't for the loading screens and bad controls, the other problems are pretty livable. They always did say you can't judge a book by its cover. This game proves that only too well.
EDIT: I got around to finishing Sonic's story, however doing so doesn't really change my opinion on the game, Sonic's story probably being the easiest of the three, is somewhat annoying due to his interaction with Elise and unlike in other stories, Tails and Knuckles make terribly brief appearances and generally lack any reason for being around at all. Even though I haven't finished anyone else yet, I'd say their story and characters are more involved and in depth than that of Sonic's.