D1 was and remains a particularly good camera
even though it's now very old and has only a very modest ~2.5 megapixel image resolution.
There are two main reasons why the camera is not yet completely obsolete. Number one is because the F5 derived body is indestructable like a tank. All the mechanical parts were designed to be good for at least 100,000 exposures, and many many D1's have shot twice that many and are still going strong. I have no problem believing that working antique D1 cameras may be found in attics a hundred years from now.
The other, more significant reason is the camera produces vivid slide-film-like color and has a very high dynamic range largely due to its very large CCD cells almost 18 microns in size, on a sensor about 85% the size of a 35mm frame.
Most newer consumer digital SLR cameras such as the Nikon D1X has a sensor of roughly the same size, but with many more millions of CCD cells squeezed into the same space. The individual cells are thus necessarily much smaller than the ones on the D1.
Although CCD sensor technology have improved much in the time since the D1 came out, smaller cells still means each get less light and have room for storing less charge. The tradeoff then becomes a limited dynamic range and ultimately more flat and video-like pictures compared to the D1's vivid shots. (Future sensors designed with ideas derived from Fujifilm's SuperCCD HDR technology may change all that, however!)
The D1 employs a very strange color space similar to but not exactly like NTSC. JPEGs written by the camera tend to have pretty awful looking skin tones and reds looking slightly purple. The trick is to use instead of JPEGs the Nikon proprietary raw image format "NEF" which takes up about 4 megabytes per image, and then using 3rd party software such as Bibble in conjunction with Photoshop to get the correct colors.