It was good, but the console version was better.
Even though this game was pretty good, I was expecting more from it. The main story was too short, the collectibles are much too hard to get, considering you have to complete time-consuming missions that must be unlocked or bought with play coins, and modern and classic Sonic's stages played pretty much the same. If you enjoy games like Sonic Rush, then you will probably really enjoy this game. Just don't start playing it thinking it will be very similar to the console version. Although it lacked in many areas, some upsides to this game are its music, and its 3D graphics which look awesome.
!!!!!!!!! A Must Buy
I'm getting this game for Cristmas (first week when Mario kart 7 comes out, getting that too) and I think this will look great. The game overall supports Streetpass, so you could share records about timing. I would rate this game 10 out of 10. :P :D