Can't recall another movie that had me still thinking about what it meant months later. It's unfortunate that people get hung up on the absurdity of a man being in love with an operating system, because that's merely a plot device to remove the usual boy-meets-girl movie cliches from the equation, so that the focus becomes, what is love itself? What is the nature of the connections we have with other people, at the cellular/neuron level?
At a shallower level you could say that the movie asks -- if there was a way to provide that chemical "fix", without there being an actual person at the other end, would people buy it? And if they did, could they still be just as fulfilled? And is that the world that the internet and social media are creating? I think those are probably the questions that a lot of people take away from it, but to me, the intent was to make you feel things at a much more visceral level, and that is the lasting impression it made with me. For example, it made me miss my grandparents, really suddenly and intensely, and made me think about my own afterlife, if that exists, and no longer being on this planet with my wife and whether our relationship will live on somehow/somewhere. I can't say I dwell on such questions very often, and I'm damn sure no other movie has made me ponder such things. The second half of the movie becomes downright hypnotic at times. I was feeling things intensely while my brain wasn't 100% processing what it all meant.