Loved, loved, loved it. Seriously. One of the best movies I've seen all year. Brad Pitt and George Clooney both play really out there characters and do it with spot on accuracy. And, the rest of the cast is stellar too - John Malkovich as an ex-spook who intones "What the Fuck" in a Rambo-like fashion throughout most of the movie, Frances McDormand as a trainer desperate to reinvent herself through plastic surgery, and perhaps most sympathetic (to me anyway) Richard Jenkins as McDormand's secretly-in-love-with-her supervisor who ends up making a very poor choice in service to that love.
Not as funny as Big Liebowski, but definitely near the top of my list of Coen brothers faves.