Pretty good game! Control is good and the music is nice when not being drowned out by the constant gunfire. The game lacks in a few major areas though.
First, the bosses take FOREVER to kill. I get bored holding the mouse button down waiting for it to die, and that's even with the best weapons available.
Second, it would be great if there was some kind of charged weapon or bomb for bosses or in areas where there are a lot of enemies. It's manageable without them, but it would add another element of gameplay.
In the end, the gameplay is solid but lacking. Maybe add an upgrade system or some kind or at least re-balance the health of the bosses. I stopped playing because I got bored waiting for the bosses to die.