The title is the joke, because in the opening moments you learn that best friends Celeste (Rashida Jones, who also co-wrote with Will McCormack) and Jesse (Andy Samberg) are a couple who married too young and are now in the middle of a divorce. The film has to spell this out explicitly, otherwise you'd mistake them for two people who thoroughly enjoy one another's company and share easy laughter over inside jokes. They still pretend to give handjobs to tubes of lip balm, for crying out loud, that's how chill they are with each other.
But underneath the protective layer of effortless rapport and affection is fear: that the divorce is a mistake, that they were wrong to be married in the first place, that nobody else cool enough will come along, that Samberg's easygoing guy actually needs the Type-A Jones to jump-start his ambition for him. It's a passive anxiety that the movie carries well and lightly. Until it doesn't.
Shot in a naturalistic style more in line with art-house standards or a small-scale studio oddity like Jeff Who Lives at Home, and much more focused on drama than any trailer would allow these two actors known only for comedy, it announces itself as something to be set apart from rubber-stamped romantic comedy. So it's strange -- and strangely irritating -- when the movie decides to allow the action to trip over itself as Celeste and Jesse each have to find their own way in the world without the other to to use as a prop. He predictably slacks around with a bag of chips. She wacky-dates. And that's a bummer. Worse than a bummer. It's Heigl. It's Aniston. And nobody with a brain wants that from a movie. Any movie. Especially from one where part of the pleasure lies in building up a kind of horror-movie need to shout at the screen, "NO, DON'T GO IN THE LAYWER'S OFFICE!" It works best as an exercise in playing on the ambiguity and wisdom of their decision. And its freshest take on relationships is its brain-scrambling statement of purpose: that sometimes, in real life, if you've got a spouse whose company you still love and with whom you still enjoy sex but with whom you have some situational/emotional maturity issues, you might not go to couple's counseling and let someone smarter than you help you find your way, you might just divorce them.
In the end, it's a kind, sad/not-sad story of keeping close while coming undone, a film determined to break apart the rules about how heterosexual couples un-couple. It looks to past comedies like Manhattan and Annie Hall for their examples of the right ways for sophisticated people to navigate emotional brokenness while still maintaining a sense of humor, and to Jones' and Samberg's own contemporary brand of lapse-into-juvenile-behavior gags to make everything sound and feel like it lives in 2012. That lip balm thing happens more than once.