Looks like I am going to be the lone desenter on this issue. Before purchasing the D2x I was looking for a replacement for the Kodak 14n I had been using for a few years. My primary goals were image quality improvements, ease of use especially in post production, and a heavier duty camera body. I tried the D200 out and pitted it against the 14n, and was totally impressed with the D200, thinking it was truly a landmark camera for the price. I did not experience any of the banding that others have had, even photographing night scenes in city locations.
However since one of my areas of interest is in landscape photography the direct comparisons with the 14n and the D200 showed the 14n clearly winning in that regard. So as much as I was impressed with the D200 in virtually every other respect I opted out of purchasing it. Next I tried the D2x and found this camera to outperform the 14n in every aspect and in some cases by huge margins, including fine detail in landscapes. In all test I used the same lenses, all of them being pro level with ED glass, Raw files, etc. But as hard as I tried there was just nothing the 14n did that the D2x did not do much better, I bought and have never regretted or looked back.
One thing the D2x does I have yet to see in any other digicam is the natural and non plastic look of images, and it comes the closest to recreating the look of film without grain of any camera I have used or owned except for scan backs. There is quality to the images from this camera that others simply do not have. And I can think of at least three reviews done comparing the D2x with the top dog Canon from top notch reviewers. In all three reviews the D2x showed better detail than the canon, subjectively better color as well.
Taken a step further a photographer from Finland I think tested virtually every digital camera made including medium format backs using the same still live and one model throughout all of the test. It was absolutely astonishing what little difference there was between the D2x and H54 using Zeiss lenses even. I doubt I would have paid $2,000.00 for the difference let alone the 30 grand plus one would have to pay to buy into a system like that. This photographer posted all of the images free for download a year or so ago. Unfortunately I lost the link. Even pro canon shooters made remarks like, "have to take my hats off to the D2x" for its performance against the medium format backs. I downloaded and kept those images as a sober reminder everytime I get the urge to spend money on a medium format back.
I hope this helps in the discussion. The bottom line is that as great a camera as the D200 is my own experience tells me the D2x is in another league all together.