I had it, i don't really think it's worth the money. I'm not totally disappointed with the game, because the controls work great. But personally I think the controls don't match up to the mission requirements, which makes most of the mission ANNOYING as hell.
I'd give it a 7/10. If you really like "hard" game, and don't mind having to keep re-doing missions, going back to beat certain missions in order to move on in the storyline and the lack of actual "music". Then i'd say go buy this game. It's definitely a pretty decent length for a Sonic game too.