In article , Chris Malcolm
wrote:

the reality is that most people don't care. they buy sigma because it's
cheap and they're happy.

very, very few people pixel peep or take pictures of test charts to see
if their lens is functioning properly. if their photos look reasonably
good, then as far as they're concerned, the lens works fine.

True, but I'm not one of those people, nor are my serious photographer
friends. That's why I'm surprised none of us have had these notorious
Sigma problems. Mind you, none of us were foolish enough to buy one of
the kinds of Sigma lenses which do have well documented problems with
our particular camera, e.g. in my case the stronger autofocus motors
in newer DSLRs quickly wearing out the gears in a couple of old Sigma
models which were obviously designed to cope only with the earlier
slower autofocus motors.

a problem that pretty much only happened to sigma. how often do you
hear of stripped gears with nikon or canon lenses, even with older
lenses that predate the high power focus motors?