Since I asked the question, I owe a great deal of thanks to all the posters. The replies paint an interesting and varied picture, and even though it's not necessarily pretty, at least being forewarned with some details makes me feel more confident that their worst is only "extremely disappointing" (my take), and sometimes they do okay.

At least there don't seem to be any incidents of pax being dragged away by the airport security police for complaining that their bags weren't on the inbound - an event that you can (slightly exaggerated) dig out of the AA archives.