Picked up 25 Panasonic CR123A (more properly, CR17345) cells from the usual eBay supplier and put one to the test:

Somewhat to my surprise, it delivers pretty nearly its full rated capacity at 400 mA discharge. It’d do even better at its 20 mA (!) rated current, of course, but I wasn’t up for a lengthy test…
Yes, the nominal capacity spec is at 20 mA (C/77) discharge: one LED worth of current. Even the pulsed spec is only 900 mA at 10% over 30 seconds, which says a flashlight really puts the screws to the poor things…