Really addicting, and with some good music to go with it
The way it works is pretty impressive, and it takes true skill to play Hard and Expert levels, even on the earliest songs. I enjoyed just playing the guitar, even if only as a video game. It was just fun, and with the music I liked (cIassic rock ;)) I was having a great time.
I really liked how it was somewhat similar to real electric guitar. This brings me back to a summer with lots of GHII, good friends, and good times altogether. This was when I spent most of my time on Guitar Hero II. I remember playing all my favorite songs from rock greats as far back as the 1960's.
The only thing is that it's not much different from the previous installment. They should have included some new aspect of it, such as guitar motions or something different.
It's really fun, maybe a 8.5/10. Just good to have around, to play with others, and just to chill to some good, fun music.