You can buy a used drum set and guitar off craigslist for less than it takes to buy an Xbox and Rock Band.
Not nearly the real thing but not entirely useless.
I remember going over to my parents house one year...my sisters asked me if I wanted to play with them. Naturally, being a drummer, I sat down at the drums (and then went to my car to grab some no-crappy sticks...and into the garage to steal the drum stool from my old kit that is still sitting at my mom's) and chose "expert" mode.
My sisters laughed and told me, since I had never played the game before, that there was no way I would be able to do it, and to choose something lower so we didn't just fail the song...
They were...kindof correct...it was harder than I had anticipated, but I still finished with a pretty respectable score.
The hard part about playing the drums on this game is that, as a drummer, the rest of the band follows you. It's really frustrating to have the machine tell you that you're off with you're rhythm, haha.
One mode I really wish they would add to the game is...like..."free play". Assign a sound to each of the drums and treat the kit like a midi controller. I know people that already do this in their home studios (although as more of a novelty than anything else) and they actually work :).
Point is: rock band is a really fun game, and playing the drums in it is very similar to playing the drums in real life. Doubly so if you've ever done any work in sequencing software. Playing rockband is like what I used to "see" as I was playing the drums after spending hours and hours in a sequencer.