I don't have RB 3, but I have 1-2, Beatles and Lego Rock Band on Wii.
Depending on the game, I can do different things well.
RB1: Hard Guitar, Expert Vocals, Expert Bass, Easy Drums.
RB2: Expert Guitar, Expert Vocals (100% Baby!), Expert Bass, Medium Drums.
BRB: Expert Guitar, Expert Vocals, Expert Bass, Easy Drums.
LRB: Expert Guitar, Expert Vocals, Expert Bass, Easy Drums.
These are based on more or less an average.
Also, yes. I suck at drums.
I would like Rock Band 3, but there are just so many games/systems that I want more than it.
Oh, and Activision discontinued Guitar Hero. O.o