Decent game. This is the first one I've rated, so I don't have a perfect reference point though...
I found that the acceleration-based movement meant that I could be moving in one direction and shooting in another, which kind of bypasses the main choice of the game.
I would recommend adding in a zombie monster that accelerates slowly like the player does, because that encourages strafing over constantly backpedaling/shooting, and it would give a more unique feel to the combat.