I had a few issues with the game, such as how the Curie was designed and also the predictable behaviour patterns of some of the monsters (especially the Proxies) or the only superficial discussion of most of the philosophical questions, but I think it says a lot that I enjoyed the game very much in spite of all that.
Especially the ocean floor exploration was just ... magnificient to say the least. The environments felt utterly unique and extremely well executed. I especially liked how sparingly animals were used and how different the later stages down at Tau felt and played. All of the ocean-bits of the game felt just as impressively atmospheric as my best moments in Far Cry 2 and Shadow of Chernobyl.
Much love