Bought it today, left work early and played for 6.5 hours...
Love it. IMO, GH3 was fun, but it has officially been DETHRONED.
Rockband has a better quality guitar (by FAR), bass guitar, drums, microphone....Rockband has much better song selection...Rockband has better multi-player & single player is ALMOST on par with GH3...Rockband has wonderful graphics (which are important to me) and....Rockband has a TON of character customization & design....
Overall, wonderful game so far--truly impressed. May sell my GH3 now.
Well, I now only have access to a PS3 & 360...Plan on buying a wii soon (lol, if I can ever find one available!) but will probably wait until some of the major RPG's come out like Dragon Quest & Tales, etc.
Anyhow, I'm so far behind in games to play that I'm not in a huge hurry (lol, haven't even gotten a chance to finish God of War II yet!)