***If you really want to save yourself an amazing gaming experience, one that you will not forgot for a while to come, I advise to know read passed this regardless of no spoilers.***
I just finished the game about a half an hour ago. I personally went on youtube and watched the ending about 30 times over to grasp the thing myself before looking at other peoples theories and explanations.
Moral of the story is, if you have not played this game, find a way to play it, and do it now. Just like all Bioshocks this game strikes a certain chord with the way games are made, and I felt myself watching a movie more than playing game. Easily one of the most detailed, intricate, and well executed plots I have seen in A WHILE in a video game. Every little thing you see in the games expansive story line all pieces together at the end and it has a huge "OOOOOOHHHHHHH SHIIIIIIIII----" moment. Also a huge "WTF" moment. I can't get over how beautifully designed this game was and it really is my top game for a while to come, I don't know how Irrational games will be able to top it. Simply beautiful.