my opinion is to always buy the new one....

in my opinion the D70 is a better camera than the D100..hands down.....even if both cameras were new in box with warranty. BUT I have definitely had to use Nikon service before and you don't even want to have to consider the cost of repairing a used camera out of warranty. They do great work but WOW are they expensive if its not a warranty repair.

both cameras handle the same in terms of AF performance...neither is blisteringly fast compared to a D2X.... but both should serve well for your purpose. I feel the D70 has far superior fast ISO performance and I always hated the D100's slower flash synch. I do a lot of fill flash and love the D70's 1/500th.

don't be fooled by the 100 in the name.... the D70 is a newer tech camera and is in no way an inferior camera to the D100.

if price is really an issue...the D50 is every bit as good as the D70 BUT its not as ergonomically friendly...not quite as easy to use in manual mode..... has a few things less than the D70 but essentially it is still a very fine camera and easily capable of taking images of the same quality as the D70/100....and it cost a lot less than the D70 new. I had the pleasure of using a friend's D50 recently and was amazed at how much camera that Nikon packed into such an inexpensive package.

The D70s is a much better camera. I have used both and prefer the D70s because of the speed of operation if not anything else. High ISO is nice and the colors are truer. One of the big gripes of the D100 is how flat the colors tend to be straight out of the camera.