I hated this movie.
As a married man I hated this movie. For better or for worse is a real promise made to each other when we marry, also being faithful was promised as well.
The fact that either of them agreed to this is just incomprehensible to me. I wouldn't agree to let my wife sleep with another man if we were homeless and he offered a trillion dollars. I'd no longer want to be married to her if she slept with him and I wouldn't want to be married to a woman who'd be willing to do it.
The entire plot was sickening (as a person who loves and values marriage).