Upload & Sell: Off
Ian, testing today confirmed your thoughts regarding the 40D and XS. I honestly didn't expect the lens to function properly paired with either body but I wasn't going to take it as fact without doing my research. The good news is the lens functioned flawlessly on a 1D MKII which means it should have decent resale value as there are still quite a few of those bodies in service.
Interesting, that seems to contradict older "common wisdom" regarding those very old Sigmas - must take note!