I’ll tell you what’s up: the Guitar Hero guitars work with Rock Band 2 on PlayStation 3.
We’re looking into what happened, but for sure we know that the Guitar Hero III guitar works in Rock Band 2 on PlayStation 3.
GameSpot has a good, slightly dated chart for other games.
We do not know if the Rock Band 2 special edition guitar works on Gutar Hero III or World Tour yet.
But one interesting twist, the Nyko FrontMan guitar that we love so much does still work with all games. However, it does not work in Rock Band 2 on “Rock Band Mode.” There is a switch on the Frontman’s receiver that selects between “Guitar Hero” and “Rock Band” modes — and that switch has to be on “Guitar Hero” in order to play Rock Band 2.