Controls fail
This game is otherwise a 9/10, but when I try to do fine movements really fast, the ship moves too much. This is troublesome when I want to move just a HAIR out of the way. Your collision detection is also hard to figure out. It takes way too long to level up, and the reward for leveling up can be insignificant (one more life container when I'm already out of lives does not help at all...)
I've seen a lot of great games RUINED lately due to oversight by the author. Games don't have to be made simple, but when you can't beat it, it should feel like you didn't deserve to, not because the controls are too brutish (see Ninja Gaiden: die a lot, still feel like you deserved it).