The one thing that bothers me/makes me nervous about the possible success of this game is the GHTV service's use of non-separated tracks and its effect on the music genre. It's more like playing over the music. Essentially you could get the same thing from customs.
I don't want to see the significance of getting master tracks diminished, and it affecting Rock Band negatively as a result, either by labels stopping giving access to them or people passing on RB tracks, thus hurting that series, because they can get these much cheaper(?). The separated master tracks are, to me, what made these games the most interesting and cool. The difference between playing a game with individual instrument tracks from the actual bands that you control versus playing along to song is huge.