Finished the Wii version. Took about 7 hours, I think.
A short review: it's a good game. It's still got a few hiccups, but it's miles ahead of what Sonic has been recently, even in Unleashed. There's even a little bit of momentum play in there (although not with rolling, just running). The gameplay is about 80-20 percent 2D/3D; the 3D sections are often "automatic" sections where you have to move forward and dodge obstacles. There were some unfair parts, especially in Planet Wisp, but they're conquerable. The story is slightly better than previous Sonic attempts, but falls short due to corny dialog (the characterization and voices are fine, but the actual jokes are horrible) - this isn't too much of a problem due to the cutscenes being skippable.
If you like Sonic in any way, I strongly suggest getting this if you can. It's not the old-school Sonic paradigm, but it's fast and fun, for the most part.