Guitar Hero Encore: Rocks the 80's defiantly helps make the wait for Guitar Hero III a bit more bearable.
But that could be the game's biggest disappointment. It is basically GH II with a new coat of paint. Heck, even the opening video was the same, only the characters were decked with 80's gear. And I will be upset if I find out the X360 version of GH II has those same 80's songs for download off Xbox Live (Of course, I'm sure GameSpot might have announced that if it was happening).
Still, with that aside, GH Encore: Rocks the 80's will defiantly give you something to do until Guitar Hero III comes out this fall.