Have not nearly played through all the songs yet, but have jumped into ones I really wanted to try.
Pro mode drums is a lot harder than you'd think it would be. Very hard to get out of the habit of hitting a tom when I should hit a cymbal.
Pro keyboard is insane.
Bohemian Rhapsody is so, so, so much fun to sing in this game, and quite hard solo. Rock Lobster is hilarious on vocals.
The game seems much more party-oriented than Rock Band 2. While there still are some hard songs in the game (Freebird), it's not nearly as vicious as RB2. Let the DLC account for challenging charts, this game is about playing catchy hits at parties. Still fun to play alone for me though, especially since pro mode makes drums new for me again.
Hope the Squier Stratocaster comes out sooner than later, I don't want to try pro guitar with the MIDI guitar.