I'm about 2/3 through F.E.A.R., so thoughts on the story and plot and general effect will have to wait (midway summary: meh). However, the game looks leaps and bounds better on my new computer than any game ever did on my four year old machine. Naturally the graphical goodies stand out. In particular:
I wasn't fully aware of how amazing the water effects were until I noticed the waves I created as I hopped in a dark pool at one point. The waves turned into ripples that constructively interfered with each other. They dissipated along the ramp out of the water. I guess Far Cry is going to have this on the 360, but it's the best I've seen from a PC. The water also reflects light off its surface, and refracts it beautifully from underneath (though I've only seen it once and it may have been a rendering trick).
You've come a long way, baby.
These are used in a volume almost like Max Payne, except they provide a tactical as well as aesthetic function. Shoot a guy in a certain spot too much, and the dust it kicks up makes it too foggy to see him. This can be used to your advantage too. Explosions cause filing cabinets to erupt with paper. Blasts that reach the ceiling have tile fragments and dust particles scattering down. Dusty corridors with ventilation fans cast beams of light out of the duct that are cut by the spinning fan blades.
The lighting in general!
It's totally unprecedented in its complexity. Every object casts a real, dynamic shadow. This means enemies coming around corners throw huge shadows on walls, and once again, it works both ways. I've been spotted by my shadow before, and I've watched for a guy to reload based on his shadow. I've even been spotted by my flashlight, as well as by the noise I made switching weapons. The optically distorted concussion blasts from grenades often start lights swinging wildly, throwing equally erratic shadows every which way.
Ok, well one gameplay thing, The A.I.!
It's frighteningly good. Disturbingly good. So good I honestly stopped talking to my roommate mid-sentence because I thought the enemies would hear me if I kept going. I can't exploit any artificialities like "it seems he can't see me even though I can see him, ha ha, take that potshot loser!" I have to play this game as if I'm playing against other people. Baddies have jumped over railings, have ran away and cowered around corners, and have spotted me based on my light and sound. One time a guy knew he was in trouble and shot the wall next to him (possibly accidentally, but he had a shotgun). This kicked up a cloud of dust and I couldn't see him anymore. Sure enough when I walked through it he had backed up and around a corner and sabotaged me as soon as I got in the clear. Another time an enemy saw my proximity grenade around the corner, and instead of avoiding it entirely, he tossed his own grenade around the corner to blow up both grenades.
Cons so far:
Bullet time has been done. It really does feel like Max Payne, but first-person and without the jumping. There's no reason not to use this mode. It looks incredible, it's fun, and it helps you out. No tactical disadvantage here like Max Payne's vulnerability as he rolls across the floor.