From what I have seen and others have said, it looks amazing...however, horror is not something I'm generally into so I will experience this game vicariously through others' experiences.
Frankly, if you ever played the "Thief: The Dark Project" cathedral level, you've already seen as much of horror as any game (and most movies) can offer, and it's not even horror genre.
Hammer haunts.... *shudder* And those
things that just walk around like regular peasants unless they get a hint that you're nearby, at which point they start
buzzing. First time I encountered one, I tried to clonk it with a blackjack before I realized it wasn't human.
Funny thing-- trying to knock a ghost unconscious doesn't work so well.
(As a side note, those last are one of the only game monsters that even dies creepily. Most video game monsters have the courtesy to evaporate into vapor, or fall apart, or reel and fall over, or explode. T:TDP ghostly peasants, or whatever they are, don't do any of that-- they're just gone. One frame they're staring at you with those huge colorless eyes, pale hands rising as your panic-thrown flash bomb hits the floor; next, nothing.)
(The hammer haunts themselves are even worse.)