I started playing Sonic Colors tonight (Two worlds complete so far) and I agree with Crafter - it is pretty good. It doesn't feel like classic Sonic, but it is fun to play and keeps things interesting.
So far, here are some pros and cons that I've experienced so far:
Gameplay is snappy and original for a Sonic title. Most of the gameplay is 2D, but when it segues to 3D it's pretty seamless and still controls great.
No fucking hubworld. Sonic has a Mario World style level map.
The dialog is actually really great and cutscenes are actually amusing in a Saturday Morning cartoon kind of way. It reminds me a lot of Ratchet & Clank's dialog & humor. Take that as you may.
Graphically, it looks fantastic. Sonic & Tails' character designs look better than they have in years and the character models are great. Leagues above the semi-lifeless character model used in Sonic 4.
It's on the fucking Wii. Maybe this isn't as much a con as a necessary evil, that evil being that focusing on one platform would improve the overall quality of the game, but it's still on the fucking Wii. I bitch it's on the Wii for two reasons: 1) I'm using the Gamecube Controller, so none of the Wii's waggle is being utilized, and 2) As Crafter said, the game is running at 30fps. This game would look stunning at a higher resolution and a finer frame rate... or at least damn good.
I don't think blowing through this game's main story is going to take too long. I'll have more opinions later.