As an Aerosmith fan, this completely sucks. I understand the prisoner's dilemma both Harmonix and Activision face, but as a consumer, and out of pure practicality, I am upset. How many toy plastic guitars can I have around the living room before my wife, as geeky as she is and as eager to drum in Rock Band as she is, says thats enough? You can't hang any more guitars on the wall, hide two drum kits on the porch, and manage two collections of track packs from different versions of Guitar Hero and Rock Band. I mean, I am saying this to myself. Both companies need to think this through. I don't believe in the Prisoner's Dilemma, that the size of the market for these kinds of songs is the same size if the both games can't play, within reason, the other's tracks. I say within reasons because there could be technical reasons why older tracks can't play with newer versions of either game, but I think you can work around that. We just went through this with HD DVD and Blu-Ray.
For anyone thinking along these lines, this is not the same as iTunes and the iPod. No matter what you buy in iTunes, even if its DRMed instead of DRM free, you can still get it out to CD and reimport to MP3 or AAC without FairPlay. With buying tracks in Rock Band or Guitar Hero, not only are the tracks locked to that game, they are locked to the console as well. I bought a bunch of stuff for Rock Band on Xbox 360, what if I want to move to PS3? My tracks are stuck, but there is no reason they should be, surely the game uses the exact same data between consoles.