i'm pretty good too. did you get 5 stars on every song on expert in GH2? i almost did... i got 5 stars on all but about 3 of them (specifically jordan, ugh!).
i've been playing the demo for GH3 and while it's fun, i have a couple gripes. first, the characters are ugly as hell, and they move like robots. that's not really important.
second and more importantly, the sensitivity has been turned way up for the strum bar. it makes no difference for most GH players, but since i'm one of the freaks who likes to flick it with only my thumb, the recoil has been registering as a 2nd note and fucking it up. i'm hoping this is only an issue with the shitty x-plorer controller, and that the GH3 controller will solve the problem.
and i know what you mean about the lower difficulties unlocking shit. i was hoping in GH3 they would make it so playing a higher difficulty unlocks all the lower difficulty treats. i played through medium in GH2 but only because that was my first guitar hero experience, i don't think i could do it now. and easy? i would fall asleep.