I've used the D1X on and off for a while, thanks to the new Li-ion battery packs.
Apart from the lack of GPS connectivity, or rather, the extremely clumsy and akward GPS hook-up, the camera still has a lot to offer. Colours are really realistic and good, when the NEFs are run through NX Studio, Darktable, or Photo Ninja. The NEF format is 4012 x 1324 pix, which by NX studio or other Nikon software is processed into 3008 x 1960 pix. Processing to 10MPix is an option and results are on the soft side. Darktable by default makes 4012 x 2648 pix images and Photo Ninja keeps the 4012 x 1324 layout unchanged. Later they can be resized to match the other alternative dimensions. Photo Ninja is able to extract more fine detail at the expense of a slight increase in noise compared to the others, though.
Combined with the AFS 17-55mm f/2.8 Nikkor the D1X makes for a functional and well handling unit, but is rather heavy as I think I'll resort to smaller lenses for it for future work with this vintage camera. Which, after being stood in my camera exhibition cabinet for 15 years, still works flawlessly.
In terms of sharpness, the D1X in fact has approx. the same horizontal resolution as the Zf (1), viz. ~170px/mm. The vertical resolution is only half that of the Zf, however, at ~85 px/mm. Thus the motif itself dictates what comes out the sharpest. Plus of course the Zf is FX format and covers a wider area than the D1X, from the same vantage point.