If you're an ultra-wide junkie, then this is the lens for you. End of.
Nikon seem to have redefined the laws of optics with this lens, according to some reviewers. It is unbelievably sharp, even at 14mm, even wide open, even in the corners. There's virtually no light fall-off in the corners, even on a full-frame D3, even at 14mm and wide open. Image contrast and saturation are excellent, and defects such as flare and ghosting are very well controlled. What more could you want?
Well, you might wish there were some way of attaching a filter; there's clearly no way of using a front filter and for some reason best known to themselves Nikon haven't provided a rear slot for gelatin filters. But we're nit-picking here.
Bottom line: this is the best possible reason to buy a D3 or D700. (Or a Canon 1Ds; we understand that there are adapters available, but we haven't got one yet.) If you have a Nikon FX-sensor camera, hire this lens and you will be amazed.