To me, this film is about...
I saw this movie for the first time last night. While I haven't read every single post on the movie, it seems that the point of the movie has been lost on many people.
Here's my take: If you are unhappy in your relationship and are looking for something else, take a moment and make sure that the issue is not with you, otherwise your next relationship will resemble this one. Allow me to explain.
Each character that strays ultimately finds that what made each character unhappy at home, made them unhappy in their affairs. Likewise, the issue that was irritating his/her spouse also irritated the new lover.
Thoughts?