Yeah, I think the guitar tracks are easy, but the drum parts definately aren't. Fleshy, unless you play drums for real, good luck. Being a music gamer myself, I figured "yeah, I can deal with 5 notes at a time, whatever." and jumped straight into hard. I failed so fast it wasn't even funny.
But Rock Band definately isn't a fun game to play by yourself. Unless you have three or four people to play with on a regular basis, I wouldn't recommend getting it, but if you do, it's impossibly awesome. I definately agree with Eggman, just because a game is easy doesn't mean it sucks. Look at Audiosurf, I picked up playing Ninja Mono in approximately 30 seconds, and proceeded to start setting high scores on things. Doesn't stop it from being one of the funnest games I've played in recent memory.