I liked this movie, notwithstanding that it's sad to the extreme: the scene in which George is told over the phone that his partner has been killed in a car accident -- and that George is not invited to the funeral -- is one of the most powerfully emotional scenes that I've seen in a long time.
The movie is based on a book by Christopher Isherwood, who I had not previously heard of and who was one of the first writers to address and examine homosexuality. The story is as much about emotion as plot, and Colin Firth does an amazing job of conveying one person's emotional life, including the way in which your feelings can change not only during the course of a day but even during the course of a conversation.
George is an English professor and appears to be in his early 40's; he was with his partner Jim for 16 years, and the short scenes where they're shown together (in particular, the scene in which they are reading together and talking about their dogs) convey their closeness, connection and affection. He's also got a quirky, ambiguous (?) relationship with Julianne Moore's character, who wants the two of them to be a couple following Jim's death.
The music in this movie was perfect - it was the polar opposite of the Avatar music (my critique is here), which didn't add to the images at all. Here, the music complemented the emotion without being melodramatic, and it made me appreciate the film medium: I don't think I'd have gotten as much out of the story either reading it or seeing it as a play.
The director of A Single Man is Tom Ford, who I read this morning was formerly the creative director of Gucci. The Gucci connection makes sense given the beautiful aesthetics of the different scenes (excluding a few that went over the top, as per Manohla Dargis's review: "at times Ford's taste seems too impeccable, art-directed for a maximum sale, as in a black-and-white flashback that brings to mind a perfume advertisement").
Movies, like books, work for me when they get me on multiple levels: mental, emotional, funny-bone, visual, musical, appreciating the art of acting, etc. This one does that; it's a well-done work of art.