I love the Coen Brothers. I have loved every movie they have done except "The Ladykillers", which I do not know why they did. It's like remaking "Gone With the Wind" or something.
Anyway, I'm happy to report that "No Country for Old Men" has taken the Coen Brothers back to "Blood Simple" and "Miller's Crossing" territory with excessive gore and a great story.
Javier Bardem is a totally ruthless killer and Tommy Lee Jones personifies the real cop, meaning that Bardem gets away with it, and Jones can't find any clues. This is what makes the film disturbing for people. They hope that "CSI" would come to the rescue.
If you are not a Coen Brothers fan, or if you aren't familiar with their work, I'd suggest starting with "Fargo" and "The Big Lebowski", arguably their two best films. Follow this up with the aforementioned "Blood Simple" and "Miller's Crossing" and then try this, and you will be deeply impressed.