What makes this lens unique is that most lenses perform their best about two stops down from wide open. Typically fast lenses are not very good when shot wide-open. They tend to have terrible falloff (vignetting), an overall lack of sharpness and increased abberations. This lens, like its predecessor the 58mm f/1.2 Noct-Nikkor, is supposed to perform equally well wide-open as it does stopped-down.
At $1,700, this lens is a bargain compared to the $3k-$3.5k that used 58mm f/1.2 Noct-Nikkors are selling for.
On a DX body the equivalent focal length of 87mm should make this lens an outstanding choice for portraits.
Can't f1.4 too shallow for portraits?