I use it occasionally and have had some decent luck with it. I normally expose at EI12 and develop normally using the dedicated developer.
I picked up some in 120 roll film that I want to shoot in my Bessa II but I haven't gotten to it yet.
I do like the film and to me it resembles PanF a little bit.
CMS 20 requires some careful handling. Keeping contrast under control is important. I always use a tripod, I prefer to expose in overcast conditions to help reduce contrast, and I am very careful with my temperatures and times when developing. I have also observed that this film prefers lenses like my older, uncoated, Elmar 50 rather than the more clinical ZM Planar 50. When it works the resolution is awesome and the film has an awesome range of gray tones. I'll have to dig around and find some of my photos to scan.
I agree that it can be a bit of a bugger to work with, but when you do it right...WOW!