I watched this game live at
ChessWorld and Kramnik's knight sacrifice in move 13 seemed to come as a big surprise to everybody. This game was certainly the one I enjoyed most in this tournament so far, even though I had a hard time understanding it (and still have). There are many moves from both sides that simply seem to be beyond my comprehension.
On the other hand, I watched the post-game press conference (you can find it at ICC), and it seemed that even Kramnik did not calculate the sac through. He just said that it felt right or something like this.