the only annoying thing is that the CV 40 1.4 uses the 50mm frameline on a Leica M, you can file the metal mount on the lens for it to load the 35mm frameline but I'm not confident enough to do it myself.
I have the CV40/1.4 and use it on the M9. My take on it is it's not the right lens if you're looking for good across-frame performance and good micro contrast. Wide open it has a fair amount of SA glow. It has fairly strong field curvature. Background rendering can also be busier than a lot of people like - basically the opposite of the 50 Lux ASPH and Sigma 50/1.4. I like it for people photos or those times when you want a gentler feel to the image.
