DFW is fairly large, not sure how far you'd get walking.
When's your flight and {edited-Doh!}?
Six hours is a long time to hang out in an Airport. An hour was long enough for me in Denver.
Hell, if I'm in the area that day, I wouldn't mind swinging by there or something.
Running to the DFW every weekend seems to be a habit of mine now. (World Cup party next Friday in Dallas!)