The price of the Voigtlander 50mm f/1.1 is one-tenth (1/10) the price of the Leica 50mm f/0.95 ASPH Noctilux-M-ASPH.
Which means that anyone owning the Noctilux might consider the Voigtander offering as an accessory, one that just offers a different style of rendition (presumably lower contrast with more aberrations, which has its pluses for some subjects).
The practical issue is that a 50mm f/0.95 Noctilux-M ASPH has not been in stock anywhere that I know of for a year or so, and the waiting list is likely a few years long. Therefore, any Leica M user lusting after the Noctilux might reasonably buy the Voigtlander 50/1.1 as an interim solution.
I’ll be studying the ergonomics and optics of the Voigtlander 50mm f/1.1 and adding my findings to my Guide to Leica. Of course, since I also own the Noctilux and have used it extensively, I will be able to comment on the Voigtlander lens from that perspective.
The following description is possibly incorrect, the Nokton 1.1 might not have an aspheric element, though it does have half-stop clicks and a 10-bladed aperture. I am researching this issue.
The Voigtlander Nokton 50mm f/1.1 Lens is a high speed aspherical lens for VM lens mount rangefinder cameras. The lens is constructed with 7 elements in 6 groups, accepts 58mm filters and has as a minimum focusing distance of 3.28' (1m). This very fast and sharp lens weighs less than 16 oz., features an all-metal lens barrel construction, and a 10 bladed aperture diaphragm which creates pleasing out-of-focus highlights. Click stop aperture movements at half-stop intervals makes subtle adjustments in exposure or depth-of-field easy.
The Nokton lens is unusual in the rangefinder field because of the use of modern aspherical lens element fabrication technology on the rear element. The lens is constructed with two aspherical surfaces and one SD (super-low dispersion) glass element. This maintains the high level of image quality that rangefinder customers have become used to while keeping a highly competitive price point.