It's possibly one of the best lenses ever made - incredibly sharp, contrasty, solid build quality. I don't know how it compares to a 600 or 400 prime as I haven't used them, I got it because I wanted the flexibility of a zoom. I shoot a bit of everything from sports to wildlife and couldn't pick a prime that would "do it all." This one does do it all - very well.
One thing to consider is the body you're going to mate it with. The D200 doesn't focus well on small, fast moving stuff and hasn't exactly wowed me when shooting airshows or military jets, even with good glass like the 70-200 VR
or the 200-400. However, put it on a D2x or D300 and it focuses incredibly fast and accurately. Also has a focus limiter switch to minimize hunting on low light days, plus it has a focus pre-set you can use for subjects at a fixed distance like shooting a bird's nest.
When I went to Axalp this year this was the only long lens I carried. Combined with some A.net folks' advice to another shooter (in a "should I take the 70-200 or 200-400" thread) and the lens' solid performance, I was quite confident it would be worth lugging up there. It was!
Nikon has recently lowered the price on this lens quite a bit. It came out around $7K in Canada, I paid around $6K and it's currently available new up here for around $5.2K. Well worth the money.