Sony NEX-5n Voigtlander 35mm f/1.2 Nokton
Panasonic G3 Voigtlander 35mm f/1.2 Nokton
My tests and use of this lens have proved to me that it is a very good lens indeed. Its very fast and very useable at f/1.2, and as such is incredibly useful in low light situations. However I have mixed feelings about its use as an all-round lens on the systems I tested it with. For my NEX-5n, it is quite simply stunning and in combination with that camera provides a top quality standard lens capable of extraordinary results at all apertures. It is also simple to use. However it must be remembered that this is an expensive lens, and that expenditure has to be justified.
Because of the limited nature of the NEX lens range at the moment, it will fill in a gap for me. A very fast standard lens is something that I will find a lot of uses for, especially since it also produces such sharp results at f/5.6 > f/11, the apertures I use the most. On m4/3 its not so useful for me. Partly because of the focal length it gives on that system and partly because there is already a top-class lens that fulfills the "fast standard lens" function on that system. Namely the 25mm f/1.4 Panasonic Leica, which of course has AF and is about half the price of the Voigtlander.
For my review of that lens see:- http://soundimageplus.blogspot.com/search/label/Panasonic%2025mm%20f%2F1.4%20m4%2F3%20lens%20review
As I said at the beginning, I am unable to give any opinion as to how this lens might perform on a Leica, since I no longer have my M9. I would imagine it would perform very well indeed, but if you are interested in that, I suggest that you search out a seperate review. I would provide a link myself but I don't know of one. If anyone has a link that they know of, then if you put it in the comments section below I'll add it to the post.