Wow. So, in addition to a lot that's already been published about this game, just want to throw my 2 cents in.
First and foremost, this is an amazing game. Well, more accurately, an amazing story. The narrative is very well written and executed. Even for a Bioshock veteran expecting that classic Irrational Games twist, they managed to pull off an incredible reveal for the finale. Well worth the engagement.
As for game mechanics, nothing too groundbreaking here. The game's pacing was well balanced, mixing combat with exploration with narrative. Combat itself wasn't too challenging - and the harder difficulty settings simply seemed to scale things up (ie enemies inflict more damage, you less, and on occasion they throw in an additional troop or two).
One thing I found odd, is that for a game which was clearly put together very meticulously, it seemed rather callous to make gear attributes random. I suppose that's to add a bit of replayability, but just seems weird.
Anyway, for anyone who has not yet played it: go for it! Or at the very least put it on a must-play list!