where to start
I like this game. I didn't love it. It's great, not fantastic.
First off, balance issues. Tell me why the boss levels are so much easier than any normal level. Later in the game, the enemies have an ungodly amount of health, making the game mostly boring. After the third boss. Why not try making the enemies harder to hit? More powerful? Anything besides just giving them more health.
Secondly, drops. The money drops are mostly worthless, and help in little else besides restocking arrows and health. Also, if the enemies can drop entire fucking weapons (bows), then why never any arrows? As far as bosses go, you've made it so that the drops are so random a boss doesn't drop anything a lot of the time, which is COMPLETELY unsubstantial.
Third, maybe a better quality control? With so many painfully tough enemies on the screen, it bogs down really bad.
This game needs to go back to the drawing board. I like the idea, and the upgrades and whole system worked, but crunch your numbers, man.