ATL used to have a fancier place in terminal E with good pasta salads and panninis. I'd get some exercise by walking there on my Airport productivity breaks and enjoy the relative vacancy of the international terminal during the day.
Hands down "Gordon's Galley" in IAH. Can't beat the food for the price. I like the baked potato stuffed with sausage (my fo's don't like it when I eat this if you know what i mean).