It is rare among Nikkor wide-angles because it is one of only about two lenses that is free from barrel distortion. That means that straight lines stay perfectly straight in the image, and don't bend out ever so slightly as they do with most of the other wide angles and zooms. The only other Nikkor wide angle I've used that shares this is the fantastic and inexpensive 28mm f/2.8 AI-s. Both the 28mm f/2.8 AI-s and this 15mm have linear distortion at close distances.

When used outdoors, light from the sky will cause blue flare blobs to appear on the bottom of your image. You may or may not see this. If you have a dark enough image bottom and give enough exposure, you will. If you are indoors and there is a bright window in the scene (or even out of the image off to one side), the light from that window will also cause a big blue blob.