The Guitar Hero III Demo is now available on XBL
You can play 5 songs on all difficutlies and they have a Multiplayer option available also that I haven't tried yet.
The Songs
Hit Me With Your Best Shot - Pat Benatar
Even Flow - Pearl Jam
Rock You Like A Hurrican - Scorpions

The Metal - Tenacious D
Lay Down - Priestess
So far the game is graphically much better. The colorized note keys have a more narrow appearance and Load time between songs seems much quicker. Song titles are presented in a more classier look. Neversoft gave this game a nice face-lift
Game also now sports a note counter in the bottom left of the screen
Hammer-Ons are definetly easier but the game is still frustratingly hard, for me anyways. Still a large gap inbetween difficulties. I still can't last more than 3 seconds on a song on expert mode.