You know how sometimes in a movie there's a perfect line of dialogue followed by another followed by another, and the scene is almost unbearably fun to watch, and you remember and quote it later? I can't easily remember those moments from Up in the Air because there were too many of them. I think more than of total screen time was that sort of dialogue. I haven't had this much fun watching people talk in a movie that wasn't of the witty/silly comedy genre often, or maybe ever.
I'm not yet sure how good a movie I think it was, because it usually takes me a while for a movie to sink in and my opinion to settle, but I can say that they did not take the easy way(s) out in resolving the plot, and that even though this was essentially a movie about relationships, it still passed the Bechdel Test.