This lens, introduced in early 2013, has been eagerly awaited for years. Nikon's older D-type 80-400mm VR, introduced in the 1990s with Nikon's first-generation AF system was - is - a fine lens optically, but the autofocus was - is - sl-o-o-o-w. And a bit noisy. This one gets the fast and silent AF-S system, so it should be a lot more useful for fast-moving action such as motorsports and aircraft. Maybe we'll start seeing some black lenses amongst all the white ones at places like Brands Hatch and RAF Fairford.
As well as the impoved AF performance, with this lens you also get impoved VR performance (worth 4 stops of anti-shake compensation) and improved sharpness, especially at 400mm where the lens looks like it's going to be very good indeed. The price you pay for all that, however, is that this lens is big and heavy. It's one of the most complex lens designs we've ever seen, with 20 optical elements (more even than the 18-300mm super-zoom!). And the other price you pay is, well, the price. It is expensive. But less expensive to hire than to buy!