Good
Very good game, but there are some notes:
1) By rapidly clicking mouse you can fire first pistol almost as fast as machine gun. This helps, but it looks like a bug. On first stages you can just rapid-click at the door and zombies won't be able to even come close.
2) Too bad corpses disappear with time (i think in first part they didn't, or it was more difficult to notice this). Is it possible to render them onto floor picture somehow, so corpses will stay while not eating all available resources? Or maybe add some more interesting effect when they disappear, like quickly decomposing them, instead of just making them fade out?
3) Collisions are 2D (as in "Last Stand 1"), and it's sometimes seems strange when same bullet (from hunting rifle) hits head of one zombie and legs of another.
P.S. What about (non-flash) 3D first person shooter based on this idea? :)