There is a lot of really cool and polished stuff in this game. The only major gripe that I have is the boss and unfortunately I found it to be very tedious and frustrating.
If the boss was more scripted and less random I think that I actually would have really enjoyed it. Look at Super Meat Boy's "Little Horn" boss for example. That is a hard core game in which you die in one hit, but because "Little Horn" is scripted it feels more fun and engaging as players learn the patterns and gradually improve over time. Here I felt like 90% of my deaths were due to bad luck rather than bad play because of the randomness.
Other than the final boss I really enjoyed this experience a hell of a lot. Great job!