The low movement speed made this very hard to play--didn't feel very good at all. I kept playing though because the art was rad, shooting enemies to make them ragdoll felt really good and was funny, and the game reminded me of Thief.
Try implementing this controller into your game:
http://torahhorse.com/first-person-drifter-control...
With better controls, you'll be able to make the game harder in a more fair way too. Smarter enemies, etc.
Then with a bit of polish and more content, you've already got a really really fun stealth-shooter game on your hands. Being able to silently snipe enemies with your loud handgun from across the room doesn't really make sense, but it's fun and feels good. Run with that idea!