See my Fujifilm GFX wish list
The Fujifilm GFX comes complete with a high-res EVF (see spec sheet). As supplied, the EVF slots into the hot shoe for a conventional behind-the-camera viewfinder.
However, the optional Fujifilm EVF-TL1 EVF tilt adapter inserts into the hot shoe, with the EVF then slotting in on top. Thus installed, it offers 45° horizontal movement and up to 90° vertical tilt.
If I’m working in the field this tilting EVF rocks! It will be a big help when shooting on uneven terrain or low to the ground, where getting my eye behind a DSLR or Sony viewfinder is awkward. It’s a whole lot better than lying down on my stomach in an inch of water or soggy grass so I can see the viewfinder! A fair number of shots go unmade because of such limitations, particularly in wet spring conditions.
It affords shooting low angle shots with camera below me, with my head above the camera, such as when shooting low to the ground or on a steep slope, etc. Sometimes I want the tripod actually in the water, but I can’t consider such a shot given where my body would have to be to see through the viewfinder (in the water, and I’m not going buck-naked into snow melt to get the shot, I’m just not that dedicated).
The Fujifilm tilt adapter can also rotate to the side. Very nice and a huge plus in some shooting situations over the lower-resolution and built-in Hasselblad X1D EVF. Now consider (for tabletop shooting the like), a 6" retina LCD instead of the EVF... that would be slick also.
No Canon or Nikon or Leica S or other medium format camera offers this compelling usability feature*, though Sony does (add another EVF in the hot shoe besides the built-in one).
* Right-angle optical viewfinders for the OVF do exist (like the Nikon DR-6), but these are to it. OVF right angle viewfinders have very limited magnification (or none), certainly nothing approaching sensor resolution. And... right-angle only. Such OVF-based viewfinders are just not appropriate for high-res digital photography.