I really love the game. I play almost daily. There are a couple of things that don't work as smoothly as they could, imho. These may seem like nitpicky things, and I'm sure some of them are related to the fact that I am a sore loser.
Please note that these issues are the exceptions to an otherwise top-notch flash game.
1. Precision: I haven't the foggiest idea how this could be addressed, but it seems like the game is very imprecise with regard to what you do when you hit space. I often walk up to a switch or locker and find myself flipping around instead of opening it.
2. Focus Fire: The little focus fire thing that bigger enemies use is hard to avoid when a melee weapon is equipped. Usually I have to swap to a ranged weapon, jump out of the way, and then switch back. I'm unclear as to whether a melee weapon can parry the shot or not. (It just occurred to me writing this that maybe I should be taking cover.)
3. Zombies: I understand it's supposed to be hard to shake a zombie, but unless there's a trick to it that I'm missing, it seems a little harder than it should be. I often shake a zombie only to be grabbed by that same zombie a moment later, simply because they can grab me before I react to being free.
Also, flailing my fingers around in Google Chrome is a good way to get the window closed (Ctr+W) on accident.
Again, awesome game, and I can't wait for the next update/expansion!