Well I had seen all this chatter about it and the D6 from everyone here before its release but not much on the way since its on the market along with the D6 for some latest and greatest... yes there is many reasons not to buy one for sure..
In my priorities of what to buy, I'd rather get the 600/4 or 400/2.8. I use the 500/5.6e (or 800/5.6 AI-s) now as my long lens (sometimes with 1.4x tc). Then I see Canon and Sony are almost 1kg lighter for about the same price. And I start down the rat hole of if i'm going to spend that much, why not jump ship to something much lighter. The Canon/Sony 600/4 is 3kg. Heck, that's lighter than the Nikon 120-300/2.8.