This game has blown me away with its athmosphere, a horribly wonderful nightmare, in the good sense.
But also, it has everything, I mean, I think the graphics are also awesome, it has many of today's techniques. Parallex Mapping, Normal/Bump Mapping, Refraction Shaders, Real-Time Shadows, et cetera. And what I also love, it's so easy to control, just a few buttons and a mouse is all you need, no button confusion.
And the game itself... It's so scary that before actually encountering any monsters, I was terribly scared already, not to mention when something does start to hunt you.
They simply nailed it, awesome job!