Nikon published a new behind the scenes Q&A session with some of the engineers/designers who worked on the Nikon D800/D800E cameras. Some quotes:
"Some may think that the D800 is the successor to the D700, but we were looking to bring the world a whole new category of camera."
"We also achieved superb reliability with a magnesium-alloy body sealed to make it dust- and water-resistant. In addition, we used almost the same shutter, aperture, and mirror mechanisms as the D4, able to withstand 200,000 cycles, and reduced the release time lag to about 0.042 seconds for an enjoyable user experience."