The criticism that Rock Band doesn't improve musical ability or chops is simply not true anymore. I have my friend's Casio keybaord hooked up to the game (albeit right hand only charts). I have my Alesis edrums working with the game and even mapped over the MIDI notes for the hi-hat to work. There is a Squier coming out for the game in March.
Aside from this, what's with the prevalent condescension towards music games? I personally don't like most FPS games, but I don't consider everyone who plays them a numbskull.