So, I got this game as part of the current AMD promotion. Finished it today. Without going into Spoilers, I am gonna go ahead and say that, while BSI may not be the best game I have ever played, it certainly is one of the best stories in games today. It's a rather astoundingly meta narrative that unfolds here, and while I would have hoped and even expected the political undertones of the first few hours to carry through to the end (like the extended critique of Objectivism in the first Bioshock), I am rather pleased with the way the story actually played out.
Standout features of the game are certainly Elizabeth, who could have been the center of an escort mission from hell, but never goes that far (that the game goes to extraordinary lengths to tell you that yes, Liz can take care of herself is an interesting commentary on the state of companion AI in other games). Her interactions with Booker and the World are well written, and her combat role as scavenger and turret-summoning machine make her a welcome addition to the gameplay.
Speaking of the world, Columbia is one of the great gaming venues, a place that is so masterfully crafted and brimming with details that it's this generations' City 17. A great deal of worldbuilding is communicated through it, especially in the game's first few hours.
There are few things I can find to criticize here, one thing that stood out though was an unfortunate consequence of the semi-scripted behaviour of Elizabeth. See, when you're just exploring the area, she will occasionally throw you a coin she's found, or point out Lockpicks etc lying around. So far, so good. However, bad things can happen if one of those triggers hit right after certain emotionally charged moments, all of a sudden Elizabeth drops down deep into the uncanny valley, and I feel that this is something that could have been caught during development.
Still, BSI is certainly one of the best games I have played so far, and I highly recommend getting it. Just do yourself a favour and avoid spoilers, because seriously. This game should be allowed to play out its beats without a nosy player reading ahead and being not surprised at the whole thing. Trust me on this.
EDIT: Oh, feel free to discuss the story etc here. Just remember that spoiler tags are your friend.