Hey, you can't blame 'em for trying... If they had tried in the first place.
This being said, I played through the original Guitar Hero II, beat it, and enjoyed it. I had wished there were more songs after playing them so many times, but eh. Can't win 'em all, right? I liked the idea of the encore game. It mixes it up a little, gives you a few new songs to play and the like, but this was missing something... A lot of something. Something called content. Content other than just music. Granted, the game is ABOUT music, but I was just left feeling a little empty after I had beat all the songs.
Where were the bonus songs?
Where were the unlockable characters?
Where were the new venues?
And the new guitar styles and finishes? Where were they?
And the "behind the scenes" featurettes? ...Oh wait, didn't care about those in the first place, but you get the idea. They basically just took the old stuff from Guitar Hero II, put a coat of neon paint on everything, threw in some different songs and called it good. To use an analogy that's slightly out of place, where were the potatoes that go with the meat?
The music in the first place was a little bit of a letdown. I can only stands bad 80's hair bands so long before I can't stands no more. I did enjoy a few of the songs though. The Dead Kennedys was a particularly welcome addition for me as well as others.
This all just felt like a rushed attempt to get some extra cash before Guitar Hero III and Rock Band come out, or maybe just an attempt to keep us held over until said games come out. I might not have complained as much had it been a little cheaper.
All in all, I think the reason the game didn't appeal to me as much as it could have was due to the type of music included, I couldn't stand much of the 80's the FIRST time, music included. But you know, if that type of music is your thing, this will prolly appeal to you despite the lack of content.