1st opinion is that the game is GREAT. A hybrid of HalfLife 2 and Doom 3 . It feels and looks alot like HL2 which is merged well with the creepyness of Doom 3 .
So far I prefer it over both above games since I found that they missed each others strengths (Doom 3 missed playability and HL2 never really spooked me or felt like my life was in danger ...this is F.E.A.R.s biggest strength )
The reason for this fear of being killed (excuse the pun

You find yourself backing away from fights cos the AI actually seem like real players. Theres often multiple routes to some rooms and the AI will use these routes to flank you and sneak up on you and gunbutt you in the Diet Dr. Pepper LOL . BRILLIANT .
I havent really mentioned the paranormal activities .... it is very Ringu/Ring-esque . This is great for me cos these are the only types of horror that kinda freak me out in movies etc... as you can imagine in a game with such great GFX and Audio it is even more freaky . who isnt afraid of a little girl that can boil your blood out of you just by lookin at you!!

Anyway Im off to face my FEAR.