IGN did the gaming world a great service this morning. The website compiled an easily searchable database of every song in Rock Band 2, ordered by difficulty on each instrument. It makes amazing reading and/or planning for the release of the game this fall.
Some interesting tidbits: Bob Dylan's "Tangled Up in Blue" has nearly the easiest drum lines in the game but the very most difficult vocals, and Eye of the Tiger is easy on every instrument, making it the spazz's choice in Rock Band 2. Judas Priest's "Painkiller," on the other hand, is the hardest overall song to play. METAL!