This has actually been covered roughly a zillion times, for example:
http://www.flyertalk.com/forum/trave...lown-into.html.
That notwithstanding, my best airport experiences were SIN, HKG, and DCA (Giving props to my home airport. Don't know why, but I love it...). My worst experiences are IAD (Slightly less crappy since they demolished the G concourse...), LAX, and FCO. DPS was close, but it is in Bali, so I'll give it a pass.