So like many people I started a new game immediately after finishing the first run. I'm still pretty early on but I'm already amazed by the new meaning a lot of events and dialogue take on in the context of the ending. For instance, when the Luteces are rowing the boat in the very beginning, male Lutece insists "No, he DOESN'T row." The first time I took this to mean that I Booker was a VIP and they were not to let him row. I realized instead that they must already know how every permutation of this scene will play out, and they know that Booker does not row in any of them.
Of course, the baptism scene in the beginning takes on a new meaning as well. Comstock has a few Voxophone recording in which he muses about the fate of the sinner when the baptized man emerges from the water. I initially dismissed this as a mildly interesting, if confusing, theological thought experiment. He's actually tying his knowledge of other dimensions into his preaching.
Has anyone else noticed any fun new perspectives on events in their second playthrough?