REALLY GOOD.
It's hard to make a good puzzle game that doesn't get boring after awhile. This one got me hooked from the start. Plus, it's very simplistic; thats a quality that I really like in puzzle games. My one complaint, if you can even call it that, is the unlocking of new songs. If I really wanted to unlock new songs I'd mute the music and bring up iTunes. That's only a minor gripe so you still get a 10.