So I got the Guitar Hero 3 Demo yesterday, and it rocks just all the other Guitar Heroes have. The only major thing that's different is the layout, and the timing window (mainly hammer-ons and pull-offs) seems to be a lot easier. I don't know how to explain it, you will know what I mean when you get the game. From what I see in the Demo, there's no reason to panic, Neversoft only made the Guitar Hero franchise better.

If you're interested, here is me playing Even Flow and getting 100% on it.