An excellent survival horror game experience, with every design choice making this a chilling immersive experience.
The monsters, the intelligent HUD design, the environments, the sound effects design ( top notch ) ..... etc etc, everything is made the right way, you will feel isolated and alone in a very hostile environments, even the characters that contact you through the game rarely meets you face to face ... so all the time you are on your own with no one to watch your back.
And while the objectives might get tiresome at the last third of the game ( Issac get this, Issac fix this, .. etc etc ) but it still manages to be fun since every task even if similar to past tasks requires you to face different conditions and different enemies so it works out somehow, probably the worst moment is when you receive the task but carrying it out is still fun nonetheless.
Then we have the vile necro monsters and hazards variety, mixing and matching those results in very intense and heart pounding encounters, not only do you have to fight monsters but you have to fight them in Zero-G and in Vacuum or even both, and the monsters aren't cheap-shots either, they are very vigilant and varied ( small, large, exploding, fast, slow, wall climbing .. etc etc ), you will need to use all you abilities ( stasis and kinetics ) and a variety of weapons to fend them off and have any chance of survivial.
Add to that few mini-games plus upgradable items and you have an excellent, replayable, immersive and very well crafted horror game, probably one of the best games i played in a very long time, now i just can't wait for DS2, if it built up upon all the good things in DS and fixed all its minor problems no doubt it will be a mindbogglingly excellent game.