I'd probably be upset if, for the past almost 2 years, they'd put any real effort into the tracklists and DLC.
The music in the GH series, and even Rock Band at the moment, has just gotten worse and worse over time. That's why it's failed... the appeal hasn't run out at all -- I still have Rock Band/Guitar Hero parties as often as I can -- but when the track lists are as dire as they've been offering, there' just no incentive to play.