Was having a discussion just now with friends and I concluded that there are 4 types of people when it comes to AF problems, see whether you agree.
Mr or Mrs "My-gear-is-perfect!"
Characterized by people who frequently upgrade camera/lenses and newbies who just purchased expensive cameras.
When their lens doesn't seem to focus properly they'll still think it's a perfectly sharp picture. Don't criticise his image sharpness or focus for god's sake unless you want to destroy the friendship. This guy usually sets his in-camera sharpness setting very high to impress himself.
Many of these people are brand fanatics so don't talk to them about how bad their brand is or smell gunpower.
However they can also be great and practical photographers at the same time as they are not distracted by camera prone problems.
Uncle bad-tech sob
Characterized by people who know that there are many problems with lenses but assume this is how it should be because lenses and cameras can never perfect and there is nothing they can do about it. To them, all these problems are norm & normal.
Some of them may have conspiracy theories about manufacturers and how they hide and reserve technology from consumers and can be pessimistic. They tend to spend less money in gear and believe in the saying "It's the man behind the camera".
A sub-variant of this type of photographer; some will stop down their lenses and almost never use large apertures since they assert "No lens is sharp wide-open".
Another sub-variant of this type of photographer are the machine-gunners; they tend to over-shoot for safety's sake.
They are effective & safe photographers as their often old-school techniques seldom result in bad pictures.
This type of people spend more time pixel peeping and meddling with micro-adjustments and get constantly irritated if their lens mis-focus even very slightly. Some less savvy of this type will visit service centres constantly and become a huge pain for staff/technicians.
They can often detect minor changes and pending death & complications in lenses & cameras as they seem to have a seisometer built into them. Never let him test your lenses or you will be left with a lasting sour taste in your mouth. They also tend to be critical against specific lenses that have tormented them in the past.
Most photographers in this group use large aperture lenses; the very reason which transformed them into chart huggers.
Unfortunately not all in this group know what they are doing. This results in more pain and unhappiness when focus-chart huggers realize that they can't seem to get their lenses to focus to their standards.
The "Lucky-go-copy" man
Buying lenses & cameras are an adventure for this type of photographer.
With enthusiasm like a zealot, they believe that there are sharp copies & bad copies for all lenses and spend time hunting & selling lenses till they are satisfied.
To distinguish them from the focus-chart hugger group, this group of copy hunters tend to reject micro-adjustments & service centre visits as they might believe that a lenses must be destined to the right body for the best performance. They tend to be difficult buyers for sellers as they can spend a long time testing lenses but with little aim and strategy, lenses with erratic focusing immediately result in an unsuccessful sales.
This guys can be a huge source of irritation to shops especially when he brings a laptop to pixel-peep images and try over 3 sets of the same lens.
For the case of canon users, they seem to know lens codes by heart and can tell you which year UU or UT are. And certainly not by coincidence, copy obsessed individuals are mostly canon users due to manufacturing variations which are believed to appear more frequently in canon AF lenses.
Which type or which combinations do you think you are?