I agree with William. For me, its all about the sensor.
I upgraded from the D300, which is a great camera. In my indoor group shots I was having challanges in low light, using two flashes (SB-800 and Metz 58) and sweating bullets at times. I never went beyond ISO 1250 fearing poor image quality for 8x10 to 11x17 images.
Low light is not a problem for the D700. Yesterday I was shooting at ISO 5000 indoors, and getting some great shots with great IQ at 8x10 sizes (i have no need for this venue beyond that size).
I am now looking forward to this fall's indoor group shots, and 11x17 prints.
D800 I still own an F100; do you think film will make a comeback?