I played this game a few months ago. It's pretty bad when compared to Rock Band or even to GH, but it's not *quite* as bad as most of the reviews made it out to be. It's far from good, but not the worst game ever made. I managed to get 580 achievement points out of it, and that was only playing the guitar parts. I think there are a few more achivements I could get if I completed a drum career, and then a couple hundred that I can probably never get because I'm not good enough on expert. I wouldn't recommend this if you were spending a significant amount of money, but for 4 or 5 bucks worth of trade-in credit, well...
By the way, I've never seen a game with a $4.49 used price before. That's the 360 price, the PS3 used price is $3.99. Weird.