If you're a slave to the rhythm, be sure to check out the "coolest drum/guitar simulator out there." DigiBand, the open source rhythm game engine, has released version 1.0. With support for both GDA and DTX format music files, the game features a jukebox mode for previewing songs before you shred, wail and strum.
DigiBand supports up to three simultaneous players on guitar, base and drums. Thanks to the efforts of its primary developer, Joe Wall, the game is extremely customizable, with support for UI themes, multiple NoteSkins (each player choosing their own look and feel for the in-game note bars) and fine-tuned adjustments to Note Speed and difficulty.
With Windows and Linux binaries, as well as fully available source code, Digiband can be downloaded from the official website.