Finished the game today on Normal, which took about 13 hours or so. I did some side quests, and didn't do others (I am planning a more completionist playthrough on a harder difficulty).
Overall, it's a really surprising, well-constructed game with a lot of really good ideas, and a strong blend of sci-fi and atmospheric horror. If people like Deus Ex, or Bioshock, or the Shock series in general, it'd be essentially impossible to not recommend this game -- one that, for these players, might be in their running for GotY.
Personally, I think it gets a little bit stale near the end once the variety of what you're doing starts to run low. There aren't a lot of "wow!" moments in the game (I can think of maybe 3), and what the game does right mechanically and with its depth it fails to make the moments when things boil down to a gun fight feel particularly satisfying. Still, that's really not the central focus of the game, so I won't hold it against it too much.
Pretty much a full recommendation for me. Great job, Arkane. And not too shabby on the PC version, either; it only crashed once for me, and performance was generally acceptable minus one or two situations of severe stuttering. I'm looking forward to my second playthrough.