I remember it being more oppressive and claustrophobic than scary. The first couple encounters are shocking, but after that, it's more just the atmosphere of decay and a feeling that the whole thing is going to implode around you that makes the atmosphere so compelling.
It has been a couple of years, though, so I could be mis-remembering.
Those of you saying that it doesn't matter that the game is 2 years old don't understand how 3d games work.
unless the game has such a high artistic concept or distinctly intentional "look" that utlilizes the limitations of current-gen graphics, the dated graphics will make the game less fun in just a couple years. Graphics aren't an issue for a game where they are used effectively for their purpose...where the art direction wouldn't have needed any greater graphical power at all to get their vision across. Some examples:
Super Mario World
Zelda: Ocarina of Time
StarCraft
Ico
Katamari Damacy
With games like this (there are lots of them), the graphics aren't limited by the hardware so much as they are limited by design. Yes, higher-resolution would help starcraft in particular, but other than the resolution, the graphics aren't dated.
Look at FPS games from just 3-4 years ago, though, and they look AWFUL because you've seen current-day FPS games. If your end goal is to look as realistic as possible, then until the graphics are so good that you cannot distinguish them from reality, then they will be distracting at some point in the future. Expectations rise. Go check out the original Unreal. It was AMAZING in the day, but now it looks super dumb. I really, really enjoyed that game a decade or so ago, but now I can't even play it because it's outdated graphics are distracting.
BioShock was pretty good, visually, but now it's starting to look dated, no matter how powerful your rig is or what resolution you run it at...
HL2 looked GREAT for over 2 years, but now the character animations have been surpassed, and they're distracting to watch.
I'm just saying. Why go to all the trouble of releasing this native for Mac at this point?