I've just got myself the new improved (allegedly!) Metabones speed booster ULTRA for my Fuji X cameras and Nikon lenses. This is the adapter that makes 'FF' lenses approximate the same focal length on APS-C sensors and provides a 1 stop light gathering boost as well. I'm interested in seeing if I can work with my Nikons as an across the board lens system with my all my cameras and base everything around them. If this works for me and doesn't slow me down too much because of the absence of AF (I'll be testing in the next few days to find this out) then I'll be selling quite a few lenses off.
My A7r works very well with these lenses and I've pretty much decided to go with the MF lenses for that, since I use the camera for high-end landscape and location work anyway, which means I'm not looking to shoot fast and loose. But my Fuji's are a different matter. I'd like to keep the wide-angle option that lenses like the above 20mm f/1.8 Nikon offer, without the 1.5x crop factor, which makes the Speed Booster more attractive to me. The focus peaking on my X-T1 in particular is very good indeed, so I'm hoping that eventually, I can pretty much have one set of lenses for all my cameras. For AF and fast work I have my Nikon Df and Leica T anyway.
Some initial domestic tests, showed that the optical quality from the Metabones is again excellent and though I don't have them anymore to compare, when I had speed boosters for both Fuji X and m4/3 before (the old versions) I was very impressed with them. I did a quick comparison on IQ with the Nikon 20mm and my Fuji 14mm f/2.8 and couldn't tell the difference, so that's a good start.
If this is successful then I may well be able to try out more cameras for review purposes. A lot of the expense is obviously buying lenses for the camera and one set of lenses would prove economically more attractive and also be useful for comparison purposes. For example, I'd love to see what the Olympus OM-D E-M5 can do, but I'm loathe to invest in lots of expensive m4/3 lenses again. What would suit me better is to be able to buy the body and use my Nikons to see how it performs.
So that's the plan. I'll see how it goes. Most of my work is pretty slow paced as I've indicated, so it's really down to how I feel about lots of manual focusing. More on this as I try out the various options.