This was really fun. I liked the movement. One thing that did feel bad was enemy's dropping mutations that you can't use: as far as I could tell, Extra Health was capped at 2 of them and extra stamina at 1, so when I took out an enemy and they dropped that, it was disappointing. It might help to either not drop unusable mutations (once you get more anyway), or give some sort of (temporary or score or something) bonus for getting a capped mutation.
I also noticed that enemies seems to teleport a short distance occasionally; no clue when it happens though.