I'm going to have that song stuck in my head for ages :P It's a good song, but it's a pretty short loop for how long the game is. I did appreciate the other song for battles though, and the transition between the two was smooth.
I thought the boss and enemy AI was pretty good. I liked how clear it was what kind of throw the little dirt ball guys were going to do.
I got as far as the fight right before what I'm assuming was a double-jump upgrade, so I don't know much past there but what I did see was well done.