As far as I know, Rock Band has not yet been announced for PC, although all the accessories for the PS2/PS3 version are PC compatible right out of the box. Given that the PC can use the Playstation RB controllers so easily, I think it's only a matter of time before they announce a PC version. With Guitar Hero 3, there is a PC version availible, and it's possible to play it with either the Guitar Hero Xplorer controller, or the Rock Band Stratocaster controller. I'm not sure if GH3 is sold un-bundled, or only with the guitar. I'd love to get my hands on an un-bundled copy though, because I own two PS3 Stratocaster controllers and IMO they are superior to the GH controllers (plus, I don't want to pay to buy a 3rd guitar I don't need).