I think that there were a FEW Nikon D2x cameras that did have a focus problem initially. On Nikonians.org there were reports of some that still would not focus well after careful tripod testing.
But, I also think that the MAJORITY of reported focus problems were from new users having a hard time dealing with a sensor that resolves nine times more than the human eye. The slightest movement while the shutter is open affects the very high pixel count of the D2x by blurring the image.
Also, I think that many do not understand the use of Focus Priority, and what "a4" "Focus Tracking with Lock-On" is all about. I wrote the Multi-CAM 2000 article, and have since received a LOT of e-mail telling me how their cameras wouldn't focus well for them before they applied the information in the article, but now is working just fine.
New technology has its problems, hardware and/or user based. Even the Canon 1DS Mark II (16.7MP) users reported similar problems with focusing. These new cameras resolve more than most lenses can deliver, and are much more sensitive to camera shake.
Plus, with the 1.5x lens factor, the camera requires 1.5x the shutter speed to stop "shake" motion instead of 1.0x times the shutter speed. I think a lot of people did not take that into account, and see the resulting blur as an "out-of-focus" condition.
I know that I did not take very good pictures until I had shot about 1000 images with the D2x. I studied why I was getting bad images, and found that I needed to upgrade my camera skills to the level of the D2x. After that my images became much nicer. So, I wrote this article to help others:
Understanding Nikon Multi-CAM 2000 Autofocus
My take is that maybe 1 or 2 out of 1000 Nikon D2x cameras actually have problems with autofocus. And, I realize that the most vocal group are those with real problems, thereby damaging the reputation of one of the most marvelous cameras ever invented. I can appreciate their pain. If my D2x didn't work right after I paid $5000 for it, I'd be pretty upset too. But, my experience is that MOST of the people who were having problems that apply the article's suggestions get an immediate resolution to their apparent focus problems.
The D2x is a great camera, and even if a number did have a problem, Nikon has fixed the problem by now, and new cameras are not affected. Plus, I have read several reports of Nikon's sending new cameras to people that had real problems.
Honestly, after using Nikon products for nearly 30 years, I am satisfied that they are concerned about giving us the BEST cameras money can buy, and will work to resolve problems when they occur.
Keep on capturing time...