If you haven't seen it, you really should. There's a lot to like about it, but I've noticed that the critical consensus has focused on the slickness of it, the vacuum-packaging. Many critics see this as an aesthetic flaw, but I think it's one of the elements that makes the movie so insightful.
Up in the Air is about the late 2000s in a way that few movies are ever "about" the era in which they're made. Plenty of movies get made about epochs after they're over, but more often than not, they're nostalgia pieces that use the scenery and images of the time as pure eye-candy. Many other movies get made at a certain point in time, and make no attempt to disguise their origin in that time, but never really attempt to capture anything essential about it.
The mechanically warm quality of Up in the Air is absolutely essential, as it's a story about travelers moving through environments that have been created in labs to simulate coziness. At one point, George Clooney's main character, Ryan Bingham, points out how, when he swipes his credit card to pick up his ticket at the airport, the system prompts the agent behind the counter to say, "Welcome back, Mr. Bingham" - as though he's a regular she's seen dozens of times before, even if they're total strangers.
The movie is constantly noticing the ways in which our environments are created and designed, rather than allowed merely to come into being. It does this without judgment: not only does Ryan prefer his environments mass-produced, the movie almost convinces you to see the wisdom of his approach. After dozens of elegiac shots of airport windows and hotel rooms far more inviting than his own apartment, you begin to see the beauty in the everyday.
Of course, the plot of this movie centers around Ryan's job, which is to travel around the country firing people. Any movie "of the moment" has to engage fully with the economic realities of life in the worst depression since the Great Depression, and this one does so, but there's so much more going on here. Anyone can make a movie about a recession, after all, but it's much harder to tell a story about a time that perfectly captures that time, right in the midst of that time.