Lol, I'm not getting RockBand, unless they fix the guitars! Seems like the down-strum for the guitar is messed up. (: I played it on my sisters boyfriend's xbox 360 (yes, I'm jealous), and well.. his down-strum was being lame even when he bought it two days ago.. So, I searched it up, and it seems like many people have this problem.
Here, check this out, if you don't believe me! Scroll down to see what others say..
..and if they DID fix it. Which I doubt it, because my sisters boyfriend bought it his on Dec. 29th.. Hmm.. then again, it's on the Wii.. So the guitar might be different? O_o! I don't know!