I just finsihed developing my first six rolls of Adox CMS 20 about a week ago and I won't deny this film is quite a challenge to get used to. Personally I enjoy a challenge so I suspect I will be shooting more of this stuff but I wouldn't expect to get great results right away with it.
All six rolls I did were done on 120 film. On all six rolls I did meter for ISO 20 and bracketed really heavily, two stops over and under. Letting in one extra stop of light seems to have been the sweet spot in almost every case so for me the working ISO was about 10. I used the Adotech CMS II developer and I didn't bother adding water after each roll to keep the developer from going bad. Instead I just developed all six rolls in one sitting at the Adox recommended times and temps for ISO 20.
My results were pretty good and and contrast was under control for the most part. Granted, I have the advantage of living in Oregon where it is overcast almost all the time so I get to work with very even lighting.
I think the next time I try this film I would like to give it a go in 35mm. In my case I was using an RB67 with a lens that had a maximum f/stop of 4.5 which meant I was always using a steady tripod and limited to scenes with zero movement. Even a tiny breeze was a no-no given the long shutter speeds I had to use. In 35mm I have faster lenses which may give me a bit more flexibility when working with such a slow speed film.
By far the biggest challenge when working with this stuff was the extreme curl I got in the film after it was developed. It was near impossible to load the film in a negative sleeve or holder for my scanner without getting my fingers all over it. Really annoying. I don't typically have problems with film curl but this was an exception for sure.
If you want to see samples of the work I did please feel free to send me an e-mail to: firstname.lastname@example.org and I will point you to my blog which has a few shots posted.