I don't feel the need to write a full review. For those, go here or here. They both support unique positions that I think are worth reading. But this is what I think about the game thus far:
Awesome. I have now finished the game on hard, and so I've had a chance to play through all of the main songs. All-in-all, I think this time around, the game is a lot easier. As I mentioned in the comments, the game initially seems a lot more difficult. It seems that way because there are more notes, more solos, and they come at you in various places. (Some songs, for instance, will start with a solo; GH1 almost always started with some standard guitar riff before going into a complex section). However, now that you don't need to hold the lower buttons down while playing for hammer-ons and pull-offs, the game ultimately becomes easier. I was able to blast through hard without ever losing a song, and I have 5 stars on over half of them. But, really, is this a bad thing?
The answer: no. And this is why. I enjoy playing this game for multiple reasons, but one of the main reasons is that I feel awesome when I play through a song well. And I feel even better if I play through a complex song well. It gives me that fantastic delusional thought that I can rock out to "Freebird" on the guitar. So, give me more notes to play, make it look absolutely insane, make it sound awesome, but then make it slightly easier to nail every note, and you've got yourself a happy gamer.
All that said, I'm thinking that expert will be quite a jump up in difficulty, and I'm looking forward to getting my ass kicked, so that I can use the practice mode a bit more. There are too many unlockables to be disappointed in the change of challenge. (You can unlock different guitars both by beating a difficulty level and getting 5 stars on all the songs for a difficulty level. So, once I'm well into expert, I'll probably go back and attempt 5 stars on all the hard songs.)
Before I end, I must complain about one thing that no one else seems to care about. Why the hell would you be playing Allman Brothers' "Jessica" or Heart's "Crazy on You" on the Vans' Warped Tour? The location and the song list didn't always match up, and it weirded me out. But, hell, if this is my only complaint, I'd say you've got a damn good games in your hands.