What amazes me about the movie is that Murray and Ramis get away with it. They never lose their nerve. Phil undergoes his transformation but never loses his edge. He becomes a better Phil, not a different Phil. The movie doesn't get all soppy at the end. There is the dark period when he tries to kill himself, the reckless period when he crashes his car because he knows it doesn't matter, the times of despair.
We see that life is like that. Tomorrow will come, and whether or not it is always Feb. 2, all we can do about it is be the best person we know how to be. The good news is that we can learn to be better people. There is a moment when Phil tells Rita, "When you stand in the snow, you look like an angel." The point is not that he has come to love Rita. It is that he has learned to see the angel.
Roger Ebert, Chicago Sun-Times, 2005