Got as far as the powercell and then kinda got lost and ran out of oxygen (and almost out of time). I was skeptical at first, but once you mentally map out the first few chambers, the game runs pretty smooth and once you get the tank/mask upgrade, a lot of the pressure is relieved. I was fine without the map, for the most part, but what got me was the very poor lighting towards the end, which made me lose my way at one point and I never recovered.
Still, I really enjoyed the experience. The atmosphere was spot on, movement was fine, the oxygen/time constraints made it a movement puzzle in the start which was nice.