Its all relative I suppose.. I'm coming from the point of a hobby shooter with a limited budget (extremely limited by most standards).
For a pro shooter - I can completely understand, and would likely buy the more expensive bodies. As you said, clients are demanding and you have to give consistent high quality results if you expect to get repeat customers.. I get that.
The difference, and maybe the point of my original post - is that for someone like me, who really struggles to purchase even a $5-600 body, and appreciates pro features, the older bodies aren't unusable just because tech has moved forward.
A D1 or D2 hasn't changed and will still give the same results it did when it was the "cutting edge". Your point is taken, however, in respect to better tone rendition and superior performance due to improvements in tech.
I suppose my main point is that there is a lot of life left in these older bodies and they can be a worthwhile investment for folks who cant afford the higher dollar bodies. The trade off would be, in my mind - a bit more patience in composition and / or understanding of the body's limitations(i.e. the AF issues mentioned and less crop-friendly MO sizes).
I spend a lot of time on various forums for several hobbies and see the same thing over and over again - especially in Astronomy... Beginners wanting to buy the latest and best just because that's the "hot" item. But in a lot of cases, they would be better served with an older and less expensive but still capable tool...
I read the recent post regarding the 2012 review of the D1 and appreciated it, but didn't care for some of the tone towards the end of the review.
For example: "A reader of my site sent me this. I wouldn't buy one, except as a joke."
I think this sort of thing gives newcomers a bad taste, I know it would if I had just started out and was looking for a Nikon Pro DSLR on a budget - when the truth is, I *had* a D1... and other than the color issues, I thought it took very capable pics in raw mode. I would wholeheartedly recommend its younger siblings - the d1h and d1x to a student or beginner looking for a solid body on the cheap.
Thanks to everyone for the discussion thus far - I enjoy the education on the newer v.s. older tech and associated improvements.