A bunch of news released today from E3 warrants an official thread for this game!

General Info on the game:
Wiki entry for Rock Band
Kotaku FAQ
Gamespot Article

Official Website
Official Trailer

Basically for anyone who enjoys/has played the Guitar Hero games, this will be like Guitar Hero PLUS. Bunch of new awesome songs - most of which are original recordings, 4 different instruments, online play, and thousands of songs available for download (including full albums - the first of which will be by The Who, my favorite band, and later Metallica). This is pretty much going to be the best game of its genre. I can't wait.

I think I'm most excited by the song list, and also the new peripherals. The game is backwards compatible with all the other GH guitars, but the Fender Strat they've got lined up for this game looks beautiful. The drum kit will also be a lot of fun to play around on, and is apparently a halfway decent substitute for playing the real drums. The only drawback I can think of is that playing bass in this game will probably not be as fun as it is in real life.