Well I'm about half-way through the game now and I'v got to say, it's possibly the scariest horror game I'v played. I don't remember jumping this much during a game since the original Silent Hill. The game play itself is pretty solid, the combat is very fast-paced and brutal and the strategic dismemberment angle they've taken doesn't realy get old(The necromorphs aren't the only things that can get dismembered. some of the player deaths are truly inspired, almost worth getting brutally ripped apart just to see), the 'no HUD' policy they have adopted realy helps with the immersion, your health and oxygen are shown on your character and ammo reserves are shown on the weapon so there is realy nothing between you and the game.
Visualy the game is pretty damn good, more or less what you would expect from a brand new big budget, big studio title. The setting is disturbing and fits the game brilliantly, anyone who has watched the Alien movies or even seen Event Horizon(one of my favourite movies) will feel very comfortable in this game and there are intentionally lots of little nods to classic horror movies and even some other games dotted throughout the entire title. All of the lighting in the game is based on Dentist lighting, it adds a sort of distorted and disturbing vision to everything in the game and although you can recognise everything in the game for what it is, it always looks sort of 'odd'.
The soundtrack is possibly the best I'v heard in any game, never mind a horror game, it pretty much sets the tone for everything thats going on and is often scarier than any visual element, I know it's something they put alot of work into and it realy shows, it's also a part of a program which they created for the game called the 'fear emitter' Which controls random 'unscripted' events. What this means for the soundtrack is that it changes and adapts constantly to whatever you happen to be doing and at times it can have you pretty much on the edge of your seat, yes, just the soundtrack alone. It's not something I'v realy encountered in a horror game before.
The 'fear emitter' program is a great idea on their part, it controls random and unscripted stuff happening throughout the game, whether it be a random noise from the sound of metal clanging on metal making you stop dead or a roar making you jump, to all the lights in the corridor your walking down simply going off for a minute(that was scarier than it sounds), To a shadow running across the wall infront of you making you spin around to find nothing there. etc. etc. There are hundreds of random events like this and they all add immensely to the tension and fear, which I suppose is exactly what the designers wanted.
There are also scripted events and scares in the game which are understandably bigger and better and creepier, but in the cases of the scripted events you never get quite the same sort of thing twice(unless of course you're playing the game a second time!).
The enemies themselves are great, the 'Necromorphs' as they're called =P are necro-recombinants, basically dead humans(the entire crew of the ship the game is set on) Who's DNA has been altered to make something else, in this case undead, hard to kill, alien, zombie type things. Think 'System Shock'. You can still see parts of the human features and human form, and in some cases make out where the bone has been ripped out, bent and twisted for a new use, which just makes it all the more grisly when you're cutting them apart limb from limb.
Anyway, I think I'm gonna cut myself short there. I'm loving the game so far and I'd highly recommend it to anyone who's a fan of the genre. 5 stars from me.