Awesome game, except for the drums. Find the wireless kit has some lag to it but the available songs are wicked!
The song list is fantastic and I do play real bass and real guitar as well but don't find that to be frustrating like I do with playing the GH drums. I actually find some songs easier to play on a REAL guitar than on GH but man is it fun!
The Mii freestyle is pretty crappy, great for the kids but not a lot of fun for me. I tried out the music studio and found it to be really annoying and cumbersome to setup and record anything, again, probably because I've done my own recording on real instruments.
Don't really care about the bad graphics or useless customizing you can do to your rocker and instruments, it's more fun to just rock out.
I haven't tried online play or downloading any songs but overall this is a great game to play alone or with friends, not a huge improvement over GH 1 or Rockband but still awesome.