I splurged, and got the Rush pack. It's much harder than the previous Rush songs on RB. It'll take a while to get good at them. "Caravan" in particular was so much more difficult than I thought it'd be. Cool to have charted bass solos, though
There was a post about this pack on Rush's facebook page, and it was kind of a nice surprise to see that out of well over 100 comments there were maybe 5 that were "Go play a real guitar" and plenty more defending the game.
I also got the Volbeat single. Neat song! Pretty easy, but well worth the buck.