FIRST IMPRESSION OF THE GAME:
(and I got the thing early so I had some weekendtime to play etc)
NO SPOILERS so feel free to read on..
Reminds me of Half Life 2 if you added more "Stuff" and by stuff I mean, Weapons and all these advancements to your character!
The story so far is very good, some interesting back story you hear as you progress. The sound is great, definitely play with the sound cranked on a good system if you have one.
The controls feel nice and fluid, no complaints.
I think the single thing I enjoy most is just the atmosphere the game creates, you really feel like you are in an underground world, exploring all this havoc. Anyone who enjoys action with a pinch of strategy, pick this up for at least a weekend rental to see if you would enjoy it. So far, only a few hours into it, this is definitely a worthwhile single player FPS adventure.