I used to have a D800 + the "holy trinity" of f2.8 lenses (14-24, 24-70 and 70-200) but traded them, last year, to fund my Leica acquisitions. Nothing against the D800 or Nikon, as I used them for decades, but I made a decision that I didn't want to carry around so much heavy gear and, for what I needed, my Fuji X-Pro1 was sufficient.
I'm sure you'll adore the D810. I have several friends who use them and they've proven the D810 capabilities are immense.