I was amazed how fast and responsive the D810 is as a walking around camera. The stories I have read about having to be extra extra careful because of the pixel density of the sensor are not true. You do not have to be extra extra careful, you have merely to be extra careful.
And, since you can crop away more than 60% of the image and still have a suitable web resolution image, you do not have to be on top of your subject of interest to take a shot.
D810 with Sigma 50mm art. Can't beat that!