Thanks AFB and yes, I'm lucky to get one so soon. For me it was an easy decision to sell the D810 to get the D850. My D810 had a lot of much loved use was showing signs of wear.
Focus shift is very easy to set-up and is fast. Set the perameters in the menu including the "silent live view" electronic shutter option then press start - all using the touch screen. The only catch is knowing what perameters to set but that will come with practice I suppose.
The one small problem I've noted with the D850 so far (my problem not the camera's) is that I've never shot any camera using live view for a number of reasons but primarily because I need reading glasses. I adjust the viewfinder diopter to my eye and I'm good to go with all the information I need. The D850 has a number of great features, including the tilt screen for low level shots, that make live view a good option at times and this means I've got to remember to have my reading glasses with me. Very much a first world problem I suppose and I think I'll manage.