As a writer, this is perhaps my favorite category. As I said about the Best Adapted Screenplay, though, you can't really tell who will win because you just haven't read the screenplay. However, based on the merits of the film, I think that this award should justly go to the best dialogue writer in Hollywood: Quentin Tarantino.
The man can just write good stuff, and in his first foray into the past with Inglourious Basterds, he continues his penchant for catchy dialogue in about ten different languages. Being set in Nazi-occupied France, we are treated to a cornucopia of different languages, from French, to German, to Lt. Aldo Raine's drawled English. And amidst all of that, Tarantino makes the dialogue so tense, so tight, that you can sit through a twenty-minute scene of pure (subtitled) discussion and still not get bored. That takes talent, which Tarantino has to spare. If he doesn't get the award, I'll be surprised.
The only real threat to Basterds' victory is The Hurt Locker, penned by Mark Boal. Unlike Basterds, The Hurt Locker isn't really reliant on dialogue at all. In fact, it spends most of its time in tense bomb disarming scenes, which are more the result of Katherine Bigelow's furious directing than Boal's writing. However, Boal does convey the theme of "war is a drug" rather well, and there's a little bit of potential for an upset.
Other nominees, The Messenger, A Serious Man, and Up don't really have much of a shot, though they are all very well-written. They just don't stand a chance with the competition.
[...] Best Original Screenplay [...]