I'm a big fan of the bouncing bullets mechanic. I'm always partial to mechanics that leverage the game environment/map in some way, so kudos to you!
The only small letdown was in the boss fight. Since the boss was hard to approach and there were no objects in the middle of the level to bounce bullets off of, I felt like you couldn't really use the bouncing bullets effectively in that fight. Whereas for such climaxes I expected the player would need to use the game mechanics even more than usual.