The Voigtlander Color Skopar 35 f/2.5 and Nokton 50 f/1.1 were my first lenses purchased when I took the rangefinder dive. Paired with the Leica M4-P, the Nokton and I made magic together.
In low light, the scenes were magical. Shooting on Kodak Tri-X film, my real-world photography had a creamy glow and rendering that I simply had never seen before on my Nikon SLR kit. With Neopan 1600, I had a very high keep rate from my sister's wedding; many of the photographs are very special to me and my family.
For me, this lens represented an amazing value for performance. I did not fetishize Leica beyond what it was: well-built hardware with a great quality, small lens system.
I sold this lens.
When simultaneously learning sunny-16, rangefinder photography and using film after a 10 year hiatus (of which previously was only point-and-shoot work), back and front-focusing issues was not something else I cared to add to the mix. A summilux replaced the lens.
Later, I purchased a Leica M8 and thought to give the Nokton a second chance. Unfortunately, this lens also seemed to focus behind the subject. I did not have tolerance for the lack of spot-on focusing and returned it. With such a narrow depth-of-field at f/1.1, back-focusing meant in-focus ears, or hair.. but blurry eyes. I was spending too much in film development to waste negatives/scans on out-of-focus photos.
If someone told me these focusing problems were fixed, I would buy the lens immediately. If you have the patience to understand the lens and know how to compensate for the missed focus, get it. It's awesome.
Lately, I have gravitated away from being obsessed with shallow depth-of-field. Perhaps it's a mastering of my technique, or an evolution of my abilities as a photographer. I am strongly considering a kit (21-50-90) with an f/2.5 maximum aperture -- and one lens, an f/1.4, for those dark moments.