Keith,
Of course there are photographers who are "over concerned" about their gear (not that there is anything wrong with that). But the fact is that quite a lot of body/lens combinations are simply too far "out of tolerance", to meet the sharpness needs of many photographers. For proof of this I simply point out that EVERY manufacturer of DSLRs now has a Focus Fine-Tune feature in at least some of their cameras. Why would they do this if there was not a problem. I could see ONE mfg doing it, but ALL? Surely when Canon (the first to put in this feature) introduced Micro-Adjustment, the best thing Nikon and the others could have done was to simply state (hopefully truthfully) that their stuff "works" out of the box, and that is why they do not have or need this feature. But no...every mfg added it because they saw it as a needed thing. I can assure you that they would not do this casually, as their support lines are asked about micro-adjustment a lot and that support costs a lot of money.
Anecdotally, I have countless customers that have told me how much better their gear performs after their use of LensAlign (whether they could have adjusted with another method is irrelevant to this part of the discussion).
And, factually, the genesis of LensAlign (the need) came from 2 observations on my part. One was how frustrated people seemed to be (on the forums) about their lenses front/back focusing, with no relief from the mfgs. The equipment went back and they were told that it was in spec, or they were told that something was adjusted, but in either case the owners could not verify the results, because they did not have a systematic and repeatable approach to testing the performance of the AF. The other observation was in my own photography (Canon 1D at the time) and being very unhappy with the sharpness I was achieving (or not achieving to be more accurate). In the end I tracked it down to the AF system.
So LensAlign was not a child "gizmo" for the micro-adjustment crowd. Micro-adjustment did not exist when I began the LensAlign project. The purpose was simply to provide a repeatable methodology for people to test for back/front focus errors, as a help for discussion with the mfgs about their issues, and a validation (or not) when equipment came back from the service centers. Towards the end of the LensAlign design process Canon introduced Micro-adjustment, and I was immediately on the phone with Chuck Westfall telling him of my soon to be released product, and had many discussions with him to keep him in the loop and gain his insights for the final design phase.
I have also done many demos with high level Canon (and other mfgs) personnel present, where of course I discussed the issues of front/back focus. At the conclusion of these demos I invited the people from the camera companies to correct any mis-statements I might have made. Never has any camera maker disputed the existence of the front/back focus issues or contradicted any aspect of my presentations.
I believe that the issue (con or no con?) stems from this...
A specific camera/lens combination can perform "in spec" but still have a front/back "issue". By issue I mean the following...let's say that at a given distance the combination has a DOF of 6 inches. We will call the range -3 inches to +3 inches. If the camera/lens focuses anywhere within that range, it is generally considered to be in spec. That means that the point of sharpest focus could be at the -3 point with all 6 inches of DOF towards the back, or at + 3 with all of the DOF towards the front, or anywhere in-between. Many photographers are not happy with that wide range. They want there point of specific focus from the AF system to be centered as it should be for optimum overall performance (yes, I know that most people think that DOF is 1/3 front and 2/3 rear, but that is only true for distances as they approach infinity).
Canon says it like this...
"AF precision is adjusted for the camera and lens to fall within
the lens' maximum aperture's depth of focus. However, there
are users who want to adjust it more minutely. They have
had to go to a Canon Service Center to have it done.
AF micro-adjustment is a feature developed for these users.
The user himself can now finely adjust the AF focusing
position. The adjustment range is ±20 steps in front of (-) or behind (+) the point of focus."
I have spoken at length to service centers and rental companies, as well as a few :>) photographers. Front/back focus issues are real. Some can be "fixed" using the AF fine tune in the cameras, some can only be fixed by the service center, and unfortunately some cannot be fixed. And of course, the majority of camera/lens combinations work just fine out of the box. But the minority group is large and affects a lot of people.
I hope that the above adds to the discussion of the "con" aspect of AF adjustment in DSLRs.
Michael Tapes