Okay! Let me see...
Okay, as for a review. I think this game has much potential for evolving.
First I will start out with what I found positive. The background music matched very well to the settings, was not too high-pased so it matched the mood of the game. I like sound effects of weapons, explosions, monster sounds. Aiming worked fine and so on, so generally it was all pretty good.
Still, there is a few points where I thought that I could have wanted more. Biggest thing that anoyed me, was that ammo disappeared at random. Sometimes it would lie there untill I picked it up, sometimes it disappeared right after killing the monster. Another thing is that you can't see when you will skill up in your weapon next time, not that it was important, I just thought about it. =) Another thing I thought about is.. What is the point about having such long (distance) phases, when the monsters come running the second you enter it? =) So it ends up with you killing them in the beginning of the phase, then just jogging the rest of the way to the next. Maybe you could make them a bit more stationary untill you reach them, don't know.. Also I thought that the ranged mobs with SMG was a bit overpowered. :P Hehe. They were tough to kill.
Another thing, which isn't negative is, that I noticed that you used HL2 models, actually pretty nice. :P
Still, I really enjoyed myself when I played it, and think it's actually a pretty good game. Therefore 8/10. =)