Can i just say - this game ROCKS!
For a while, you may think - its OK, then it starts to get a bit mental and Rich is right - its the sound not the graphics is where this game excells - scares the living crap out you - save your cash from your GFX card and get a 5.1 system instead.
The only game i have EVER played where im actually jumping at every sound and training my weapon in its general direction expecting to see something practically on me. Every room makes you wonder what the heck is coming next.
Not to mention the little cut scenes (in game) where the whole screen goes like blood and your left wondering WTF?
Then there are the voices - out of nowhere - whispering - "over here" -

.
Oh - and the Plasma rifle - best weapon ever? I love the charging sound it gives off and the way it lights up the room.
Loving it - so far.