Honestly, until you have used both lenses on a FX sensor, all one is doing is regurgitating 2nd hand info. I've had a chance to use two Nikkor 80-200 and two 70-200 Sigmas on my D700 as well as my own 70-200 Nikkor. On the lenses that I had on my camera, the Sigma was by far the worst compared to the Nikkors. The 80-200 was uber slow focusing and showed more camera motion artifacts thanks to no VR at 200mm F/2.8 and low light scenarios (like 99% of weddings are done in).
The Nikkor 70-200 vignette issue... well, all I can say is this:
Nikkor 70-200 at 200mm and F/2.8. This picture is a a RAW file converted to JPG and reduced by flickr, that is 100% all that was done, and has no in camera vignette control activated at all, so this is about the worst possible set of circumstances for vignetting that you can get with the 70-200 and F/2.8...
far from the black circle that was mentioned. Is it a lot? That is objective. There is nothing in the vignette area that cannot be removed 100% in either post processing or in the D700/D3 camera menu under Vignette Control... voila all gone. Personally, all my pictures get a vignette added anyway, it just looks better.
Edge clarity... no BS, I have not tested it, but Saturday I have a graduation and an E-session and on Sunday I have a wedding to do. I will purposefully use the 70-200 more than usual and take more shots to see how in real life situations it performs (I know already, but this is for the sake of testing now). I will also tack a newspaper to my fence, crank the lens to 200mm on my D700 move back until it fills the frame and shoot away. This will easily show any differences becuase if it is as bad as some people say it is, text in the corners will not be as clear as text in the center.
Having had the 80-200 and 70-200 on my D700, I can say that I am very happy that I put out the cash for the 70-200 and have no regrets. I know that if I had a 80-200 and after last weekend, I would be looking to sell that 80-200 right now and saving to move to the 70-200.
The comparison above to a 200mm F/2.0 PRIME at $5500 to the $1900 zoom is big time apples and oranges.