I got this game 3 days ago and I find it damn hard!
It's my first GH ever and I'm lost. I beat easy but even medium is hard for me, can't beat the final boss atm.
I'm amazed by all your skills and depressed by mine, everyone seems to be crazy good at Guitar Hero, am I the only one who's crap?
I love this game, it's really fun but I want to be better...
I hope I can improve but I doubt I'll ever be able to complete a song in expert. 
Remember that noob?
That was me 3 months ago. I kept playing a bit since that time but things have not changed, I'm still a noob.

I didn't play much to GH3 because well... I got it in my MGS4 period and GH3 is lucky I played something else than MGS4.
Anyway as I said, I don't play much but I still play somewhat regularly.
Ok, right now, I've done :
Easy : all 64 songs (39 regular + 25 bonus, I don't have download songs) beaten with 5 stars, last 5 stars was Raining Blood
Medium : all 64 songs beaten, last was TTFAF obviously, 55/64 beaten with 5 stars
Hard : 33/39 done
Expert : 13/39 done
I just beat Knights of Cydonia Hard tonight. Switching from medium to hard sure wasn't easy but I slowly got used to it. First 6 parts weren't too hard to beat, then I came to part 7 (Live in Japan) and that was hell.
The gap was huge, I first thought I could never beat any of these 4 songs.
But Stricken came rather easily. Then I got stuck for days...
Tonight I managed to beat KoC after 4 tries, that actually wasn't too hard, I was never really afraid by this song despite all what I read about it.
After KoC, I tried 3's & 7's and beat it on first try (whereas I kept failing the days before).
So in the end, here's where I am, 3/4 done, only Before I forget left and this one seems terribly hard to me, I'll need a lot of practice to go through I guess...
My ultimate goal really is to beat the game in Hard because I don't think I'll have any chances to beat Expert even if I was playing for years so... I wanna beat hard and go as far as possible on expert.
About expert, beat 6 more songs today + first boss, it's not too insane so far but I don't think I'll be able to beat much more than 15-20 songs in Expert.
That's it! Sorry to break this progamers thread with my noob post but eh! I thought maybe some people could care about it! (Shep, are you still playing?)