I've got a CV 35 in Nikon S mount, and while it takes nice photos, I'm not particularly happy with its ergonomics. I believe the oversized plastic ring that latches onto the lens was the after-the-fact solution to a design flaw which resulted in the aperture and focusing rings being too close together, causing apertures to be accidently changed while focusing.
I would have preferred that the aperture ring be closer to the mount where it is less likely to be accidently changed .
Additionally, the detents for the aperture settings are not very "strong" (for lack of a better word) and move very easily when the front end of the lens is touched.
I like more things than I dislike about the lens, but like virtually everything about the CV lenses for Nikon rangefinders, it has the feel of too little thought or care in its conception, planning and production, unlike all the effort being put into the Leica rangefinder program.