Many of reviewers called this a coming of middle age movie. That's probably the best way to put it. The major theme for me was that the characters played by Laura Linney and Phil Hoffman need to accept the reality of aging. In particular, they need to understand that they can't really begin to live until they put the past behind them. Many of the jokes about how retirement communities try to make their clients feel younger are effective. Brother and Sister Savage think they're getting older. In reality, they're getting better.
The whole idea of relinquishing the past to get on with the future isn't new, but Tamara Jenkins's script is very sharp, and Linney and Hoffman are perfectly matched as the cock-eyed optimist and the Gloomy Gus. They can't stand each other, but they need each other. Phil Bosco is excellent, too.