Thanks for the 'he isn't trolling' comments people. Clearly I'm not - and I have no 'status' here other than as a long term participant. I'm not a moderator, which is why I invited anyone who is to remove this if they saw fit.
Moving on. Pramote, honestly, there are few real reasons to move to a D810. Focus is better, in both accuracy, no 'left side' problem and the addition of the Group mode, which I have yet to try but people do say it is great. Shutter is a lot nicer and there is less of a shutter shock problem, plus the EFC mode in LV totally gets rid of the issue. People also commonly report no need for AFFT, which is my experience also but I don't have many AF lenses... The camera overall feels nicer.. And the ISO 64 files are even cleaner though there may be a slight penalty at higher ISO; I haven't done a side by side because I have no D800 now. The new LV is really really good and makes a big difference.
Overall it's likely to be a usability trade, not an IQ one, but those ISO 64 files sure are clean and the low ISO DR seems hard to exceed.. my best indication is that now, if I am close to home or in the studio I use the D810 rather than the A7r, especially with longer lenses and if I have a lens that fits the Nikon which is at least as good as that I would use on the Sony, but for anything under 70mm and assuming the light is reasonably good, I will use the Sony if I am straying further from base because it is still a nicer package to carry and the differences are for many use cases not relevant.
I never loved my D800e. I said so many times. It was objectively a very very fine camera but I never loved it. This one somehow feels different and I am really enjoying it. Hard to pin down why, but others have said the same... however, when Sony responds with an AXX variant that has a better shutter and better tracking focus I will probably finally consolidate in that system for good. Those are the last pieces missing from the Sony lineup that matter to me and I prefer the breadth of lens options in Sony.
ps Pramote - for sure the D800 is generally more than enough to make good pictures, especially in the hands of someone such as yourself, but the D810 broadens the 'shooting envelope' in all but stupidly high ISO situations and will therefor mean, everything being equal, more opportunities for good pictures in the hands of an experienced user.