http://blog.us.playstation.com/2008/...bility-update/
In short, all PS3 music games should work with each others' instruments in the not too distant future, bringing the PS3 into line with the 360. That means you won't need 3 pairs of microphones, 3 sets of drums, and six guitars, in order to play Rock Band, Guitar Hero, Rock Revolution, and Singstar titles.
Hurrah!
/me feels less dumb for buying GH3 on the PS3 instead of 360