Spoilers
The would you kindly twist was maybe the greatest twist in a game to date. Not only did it tug everything ruthlessly together, it satirised the very nature of gaming itself. Sheer genius.
The problem was, after that point, it wasn't as interesting. It never got the oomph back after you faced Ryan. The areas were quite interesting (particularly the final deck, with the little sister shock therapy booths and such) but it felt rather weak plotwise.
Also, for much of the game we have been mindlessly obeying Atlas, and we were punished for it with the "would you kindly" thing. Alright, we've learned our lesson - so we'll just obey Tenenbaum instead. While I heartily applaud the message and the execution of Would You Kindly, it seemed a bit... flat... once Tenenbaum took over, because the message was overruled.
Finally, the Fontiane boss battle felt as though it belonged more in a Metroid game than a creepy 1960-themed shooter. Not that there's anything wrong with Metroid, but it seemed rather out of place and made me end the game with a rather bland feeling. However, this can be redeemed due to the fact that the final levels are very much inspired by traditional gun n' gun shooters (do a scavenger hunt to get items to turn into a big daddy, protect the little sister, fight a mindless boss battle) which could be interpreted as the game's way of saying "You are in a game!" which fits neatly with Would You Kindly. It could also be argued that the LSs are in a game, in that they are in an artificial environment (the final training ground) - but they want to escape. You, also, want to escape. So the final half hour or so of the game is the player's effort to end the game - to escape the game, like the little sisters - and is kind of a game-within-a-game, seeing as how unlike the rest of BioShock it is. I'm not quite sure where I'm going, but I think it's intriguing.