Not good for casual players PLUS a few problems
This game, to put it simply, is far too hardcore for me. I mean, I felt really spazzy trying to fight all those guys and trying to get to those juuuuuuuust out of reach ledges. I gather that this was made to be hardcore. I imagine that more casual players such as myself were feeling left out. That's not necessarily a bad thing; after all, if you made it to be hardcore, then you succeeded.
I found two very significant problems, though.
A) One is the evolution of the weaponry. While there isn't anything inherently wrong with having weapons that are distinctly better than others, the Uzi and shotgun were obselete by the second level. That soon! They were just wasting time when I cycled through the weapons, and nothing but dead weight. Considering the number/strength of enemies, the weapons you get early are extremely useless.
Granted, you get a lot of ammo for those weapons, but that's like receiving a lot of bottled water to put out a forest fire.
B) Also, you get cornered WAY TOO MUCH. And if you're cornered, you can't avoid getting hurt. Not only that, but you used up most of the ammo for you better weapons, and now you only have the pistol, the Uzi, and the shotgun, which, by the way, all suck. See where I'm going with this?
This is not fun, merely frustrating and makes survival feel impossible. Often, the feeling is right.
/end critique
It's not a BAD game by any measure, but it certainly is far from enjoyable for my tastes.