I just got done with a hardcore session of guitar hero... I've gone through all of the songs on hard (not the unlockable bonus songs though), and I must say, it is HARD. Bark at the Moon nearly made me throw the guitar across the room. Crossroads drove me nuts for a few hours, but it also forced me to get better at the game and now I don't have much of a problem with it.
I play guitar, so a lot of the finger positioning came natural to me, but it still gets really hard on the later songs on the hard difficulty, lots of complicated guitar solos and hammer-on/pull-offs to do. Sometimes it feels like playing a real guitar is a lot easier because you already know what to play, rather than having to follow scrolling notes on a screen. It's an awesome party game though, we spent hours today passing the guitar between five or six different people taking turns playing different songs... It's even fun to watch other people play because it's really funny when they screw up notes, especially the sustained notes.
My pinky hurts really bad right now from playing, though.
