Not much to add, but my take is that the Nikon RFs are basically improved versions of Zeiss Ikon's Contax RFs, which puts them on the high end of the spectrum between the old "Barnack" thread mount Leicas & the M system in terms of overall usability. To echo others, the high-magnification VF is nice, especially if you shoot 50s & up, & mechanical reliability is high, but VF/RF are not up to Leica M standards. The essential usability is that of a professional system of the 1950s, which is very usable, indeed.
For me, the difference in focusing direction, etc. is not a big deal, but I started out using Contax equipment before ever getting a Leica, so I was accustomed to the basic form factor & ergonomics. I now switch between Leica/Leica copies/compatible, Contax RF, Nikon RF, & Nikon F equipment all the time & have various adapters that let me mount most of my Zeiss & Nikon lenses on LTM & M bodies.