I like HER. It's a strange and unique film, part science fiction, but mostly an interesting character study. The film takes place in an apparently near future, in which a computer program similar to Siri has gained sentience and has a relationship with her owner, played by Joaquin Phoenix. The computer voice is played by Scarlett Johannson (who never appears in the film). The brilliant script was written by Spike Jonze, who also directed. The entire cast is fabulous, including Amy Adams and Chris Pratt.
But it's really the screenplay that is the strength. It's a very thoughtful film that discusses man's relationship with technology in a very intelligent way. To say much more would induce too many spoilers, so I will leave it at that. Watch the film if you get the chance.