With the arrival of the D1x and D1h, second-hand prices for the original D1 have dropped to around the $2200 level. If you're considering the purchase of one of these cameras there are some issues that you should be aware of to help you avoid any potential problems.
This list represents a summary of the most common problems that I've heard of owners experiencing with the D1. It's been gathered from the various internet forums listed at the end of the post, and also from my own experiences with the camera and from having talked to a couple of dealers.
Also please note that, in general, the D1 seems to be a real credit to the Nikon stable. It's very well made - up there with the F5 and F100 - and isn't likely to let you down. But as Nikon's first digital SLR it does have some quirks and crotchets and some examples will have had a hard life in the hands of photojournalists.
Dust: dust on the CCD (or to be more accurate the anti-aliasing filter bonded to the front of the CCD) is a fact of life with the D1. It shows up as circular blobs in your images which grow progressively smaller and darker as you stop the lens down. The way to check for this is to take a shot of a white wall - or the sky - with the lens at f/22, then look at the result. Small dark spots in the image are dust particles: if there are a lot of them then the camera will need to be cleaned. Also look out for any other imperfections in the picture which could indicate damage to the filter from a bodged cleaning attempt: for example lines that could represent scratches or transparent blobs that could be the residue from an aerosol blower. If possible, inspect the filter by taking the lens off, setting the shutter to 'B' and holding the release so the shutter stays open and you can see the filter. There shouldn't be any visible dust, smears or other marks on the surface of the filter. If there are, don't buy the camera: a replacement CCD/filter assembly costs $800-$1000....
Magenta cast in camera processed images: not so much a fault as a characteristic of the camera. The D1 generates images in a colour space similar to NTSC when saving JPEG or TIFF files. This tends to give caucasian skin tones a noticable magenta cast (the dreaded 'purple people' syndrome). It's not an issue in RAW mode, and it can be corrected in other modes by doing a colour space conversion from NTSC to AdobeRGB / sRGB.
Diagonal banding: all D1's produce noticable horizontally banded noise when shooting at high ISOs. Early cameras could develop an additional problem that lead to even more conspicuous diagonal banding that's been aptly described as looking like the weave on a pair of Levi's. Look at the Martini bottle in the DPReview high ISO samples and you'll clearly see the effect. Cameras that suffered this problem should have been corrected under warranty since the solution involves replacing the timing electronics associated with the CCD.
As a general rule the last cameras made, with serial numbers in the range 503####, suffer far less from the magenta problem and won't develop the diagonal banding problem. My own camera, with a serial number in the 50176## range, hasn't shown the diagonal banding problem but has a definite preference for purple people in JPEG mode.
"Back-focusing": there have been reports of the camera not focusing consistently with AF-S lenses - particularly the 17-35mm. Everything looks OK through the viewfinder, but the image shows the camera has focused a couple of feet behind the subject.
Mode dial: there have been some reports of this failing, leaving the camera stuck in one mode, or not operational.
Then there are some niggly things:
The rubber covering on the compact flash compartment door tends to peel off or fall off completely.
The screws holding the compact flash compartment door in place can work loose.
The rubber plug covering the firewire port is attached to the camera by a narrow rubber strip which tends to wear thin and break.