The ending...
I'm not quite sure what I think of the ending. Yes, it was masterfully acted by Nicholson, and the scene worked perfectly.
But I felt a little unsatfisfied in the sense that we as viewers really have no impression of what was going to happen. To me, it seemed a little abrupt. Was the ending cathartic? Did Nicholson's character have an epiphany? It seemed like the emotions he felt had little connection to the other themes of the movie, except the portrayal of human relationships.
Nevertheless, I enjoyed the movie thoroughly. The slow pace never got boring, and that is a sign of strong movie-making.