Guitar Hero Aerosmith
I played through the Co-op career with a buddy (on hard). There are 40 songs (same as GH3) on the main song list and we went through them all in an evening without needing to restart a song (I suppose that only tell you about *our* skill?)
We were upset that the Aerosmith band didn't show up at all, so we played 2 songs on the single player career mode and that finally changed the models. I'll have to wait to see what he unlocks after playing through single player...
At the end of the day, it was exactly what I expected from the 5th incarnation of Guitar Hero (don't forget that there was Rock the 80's). I'll buy it if it comes out for PC.
If Guitar Hero Metallica does not come out for PC, I'm buying myself an Xbox