This really bothered me at first as well. Then I tried to figure out why. I believe it goes back to my film days, when I shot slides. Occasionally I would get something at the edge of the frame that was very distracting, often a bright spot. This bothered me to no end, especially if it was a once in a lifetime shot. When I bought the F4 with its full frame coverage in the viewfinder I was able to eliminate this problem. This has happened to me a few times with my D200 even though I am very careful to try to avoid it. With a digital camera I am able to crop this out very easily, and as it is at the very edge of the frame I don't lose a lot of pixels. Once I realized this I placed an order for a D700.
I must thank another poster for guiding my thoughts is this direction.