I don't fly all that often, but have attended a few out of state business meetings, over the past few months. My absolute favorite US airport so far is Houston. It's HUGE, has a surplus of various clothing shops, fun bars, and an assortment of restaurants with delicious choices. Its layout feels like a small city built within an airport, if that makes sense. Bravo to the designers! My least favorite I'd have to say, is LaGuardia. Just yuck. Rude people, always under construction, and not at all aesthetically pleasing. What's yours?