Extremely sad, weird, and uncomfortable to watch

Rating: 7/10 (1 June 2016)

The movie itself was actually quite good and the story was compelling due to marvelous portrayal of Theodore's conflict of heart and reason. It reminded me a little of that one The Twilight Zone episode called "The Lonely". It's almost exactly the same story except for some minor details; in the aforementioned series the A.I. has a body (it's a robot).
Disclaimer: heavy spoilers ahead. Tread with caution.
"Her" was literally a perfect example of the Zero-sum game principle in Game theory. Let me elaborate: Theodore is a lonely man who just got divorced by his wife. He buys the new AI OS and starts to fall in love with "Her". So far so good but as he excludes himself more and more from society in order to maintain his unusual relationship (without the judgment of others, that is) his OS is cheating on him behind his back with hundreds of other people simultaneously to further improve itself. So while he devolves his AI OS is doing just fine. And to top it all off even his OS is ditching him at the end. What a sad movie.
At the end of the day it's extremely uncomfortable and weird to watch a grown man fall in love with a faceless simulacrum of a woman. This is definitely not the type of movie you'd want to watch with friends or your significant other. Just don't.