@ $20 it's a steal. Do it.

Definitely...

I can tell you, honestly... is the best 3D Sonic since Sonic Adventures on the Dreamcast.

 How long is it?

Like 10 hours...

No.. the controls really suck and the camera is terrible.

Your words intrigue me and I would hear more.

If you have an action replay, its worth it. Basically you play the same stage 8 times; run though it is fun, then play again under a time limit, smash 20 pots, don't get hit once, collect 100 rings, get all 5 blue orbs... some of the levels aren't even that good, like the dinosuar level. Also, the tutorial is annoying and the controls don't work well unless you update them
If you use action replay, you can have the best controls from the get-go and only have to play each stage once. This way it become a 7/10 game that sadly only lasts a few hours :D

There is no Action Replay for the Wii.

And @OP

DEFINITELY. I bought it for $50 and I loved it. best game since SA2, maybe better than SA2, but only because SA2 had the gay Robotnik/Tails mechs. (God I hated playing as those two...)

Challenges do get a little frustrating, but they're still pretty fun...

Anyway, it's definitely worth the $20.

No. You can buy it for $10 if you look hard enough, and after Sonic Adventure 2, Sonic's been sucking. Wait for Unleashed. It might be the come back of Sonic.