we have gone over XMAS and they were not bad. Full? sure sometimes. Slow? never. they are very fast elevators. we stayed on 11? (the top non club level floor) and it only took a few seconds to get up there. there are several elevators to get on as well, and for some reason the "service" looking elevator off to the other side seems empty most of the time. people would never see it open or wouldn't get on it.
I found, in general, everyone to be really polite as guests there too, which I can not say the same for at other resorts. People let people off before getting on. People let strollers on and off first. People let families move around before moving themselves and if the elevator had 2 families on it, people didn't seem to want to squeeze in to get on. I don't know if it was because it was more realizing knowing I didn't have to wait for busses to squeeze on to or something, but I know I certainly felt more relaxed there.