I am starting to like my 50/1.2 Canon. I just got a very clean one from Adorama. Here's two at a badly-lit recital given by an amazing 92-year old pianist.
http://users.2alpha.com/~pklein/musicians/L1002312HokansonChord.htm
http://users.2alpha.com/~pklein/musicians/L1002314HokansonBow.htm
One in the car at night, just for fun. Yes, it flares, so use it!
http://users.2alpha.com/~pklein/currentpics/L1002300KatyaNiteDrive.htm
And a couple of test shots at home:
http://gallery.leica-users.org/v/pklein/album170/L1002212KatyaKitchen50-1_2-w.jpg.html
http://gallery.leica-users.org/v/pklein/album170/L1002263KatyaRead50-1_2-w.jpg.html
Not too bad! And it weighs about half of what the 50/0.95 Canon or the Noctilux weighs. Sure, I'd like an f/1 lens, but given the conversion and cost issues, I think this will hold me for a while.
These were taken with an M8, and using a 55mm B&W IR cut filter and a generic screw-in 55mm metal lens hood. I find that even in B&W, M8 pictures are sharper without the slightly out-of-focus IR component. But, you often get a half-stop more light in tungsten lighting if you take of the IR filter. which might reduce camera shake at 1/30 or slower.
Roger, you are quite right that it is an overstretched design--I think it's just the 50/1.4's Planar formula writ larger. And the f/0.95 is much the same writ larger still.
The other thing to watch out for is curvature of field. As you move away from the center of the image, the zone of focus moves forward. And I wouldn't want to use it in bright sunlight or for distant landscapes.
Still, for that extra half-stop, it's probably worth it when you need it. You are quite right that a 50/1.5 Nokton, for example, would give a technically better picture, all other things being equal. But if you're at a very slow shutter speed with f/1.4 or f/1.5, less camera shake may have the advantage over a sharper image.
--Peter, who, if he took truth serum, would probably admit he lusts for the Noctilux, but in the name of fiscal responsibility, is settling for the Canon for now.