I use one regularly with my Nikon D200 and F90X, it's a great lens, sharp and contrasty, reasonably fast focussing, (fast enough for flight shots) and is very well built, complete with removeable tripod collar. I would go so far as to say the build quality is better than the Nikon 80-400, I think you would also find it difficult to separate the resulting image quality from the 2 lenses! It's also half the price.
nirofo.