Saw it tonight...wow. It's tremendously atmospheric...there are long, silent shots of the dry and dusty Texas landscape, light and shadow are used to great affect, and the sound is haunting.
The three leads, Tommy Lee Jones, Javier Bardem, and Josh Brolin are all excellent (Bardem's character, Anton Chigurh, an unassuming psychopath with a bad haircut and a love for games of chance, is one of the most scary screen villains in recent times). The movie, for all its darkness, has some genuinely funny moments. The ending will leave some people angry, probably, as there appears to be no real resolution. However, the movie is faithful to the book (and life) in that way; things don't always end cleanly (indeed, the movie's tagline is, "There Are No Clean Getaways").
It certainly won't affirm your faith in humanity, but it is a harrowing and thought provoking meditation on the casual creep of depravity into our society. Definitely a great film and one that will have me checking door locks to make sure they're intact for a long time.