I honestly don't remember much about the music. I'm sure it was good, but I was a little more focused on other things I guess. I know I liked the few samples I've heard outside the game though.
Edit: Damnit! I just lost. Halfway through the last level of easy... Blah. Managed to get through the first three and a half levels without losing a continue, but the stupid last section of the harbour killed me because my jumping isn't as accurate as it could be. It's amazing how much easier bosses are when you aren't trying to kill them with your wimpy starting gun.