I just looked through and listened to samples of all the tracks and played a couple quick games, it's got a pretty good spread of tunes. There's some songs I've never heard before, there's many I have heard before. There's many songs I like and many I don't and some that are just tolerable. It's pretty unreasonable to assume they would ever make a music game where EVERYONE would like EVERY song in the line-up, so I'd say the song line-up is decent enough.
One thing though, other than the characters being LEGO characters, there seems to be a lot less comedy to their animations. LEGO games always had that "comedy slant" to them related to the fact that they are, in fact, LEGOs, in this it just seems like they are simply caricatures of band members and the comedy slant is kind of missing. But then again, when I'm playing the game, I wasn't watching the top screen, I was watching where to hit the notes on the bottom screen, so maybe I just missed the comedy that was going on as I was playing.
The gameplay mechanics seems laid out well enough to minimize confusion, but that switching to other instruments thing still throws me and I miss a bunch of notes in between as I'm selecting the next instrument. But it's very playable if you can get the hang of it.
I'll add it to my lineup of rhythm games on my flashcart. It seems a worthy addition, it's not like I don't have enough spare room on my 16GB flashcard. I'll get around to playing it more thoroughly eventually.