I might get shot down for this, but ATL is horrible. The timings into Terminal E are unfortunately such that several international flights come in at around the same time so you end up with massive queues at immigration and customs, with the requirement that you have to recheck your baggage after customs (rude, surly - what Southern hospitality?) has been through it.
Most pleasant, even though there is not much land-side or air-side - ORD pre-9/11. Post-9/11 LAX Terminal 2 even if the check-in area land-side is crowded, security etc are actually not too bad. I guess if you only have VS, NW and AC with a couple of small airlines sharing a terminal, there's less of a crush. JNB is actually not bad either.
Domestically, STN gets my vote for crapness, regardless of its 'revolutionary' design. It is a nightmare for me. I've only ever flown out of LGW-N, so once I go through LGW-S I'll see if my vote changes (based on previous experiences). The air bridge from LGW-N to the BA terminal is a novelty but the terminal is airy and pleasant.
S.