I have been using a CPAP machine for 13 years. I washed my nasal pillows each morning and changed tubes and other components every 4 to 6 months. I would sometimes clean around the intake nozzle and other accessible areas with 91% alcohol. I've had colds and other upper respiratory issues from time to time but there's no indication that the CPAP machine got me sick.
Nonetheless, I decided to get the SoClean 2 about four months ago. I now wash my nasal pillows about once every 7-10 days, which is far more convenient. I do this because SoClean is a sanitizer but won't remove facial oils. The machine works fine. I have it set to run for 10 minutes at 10 am every day. The ozone cycle can be set to run for anywhere from 7 to 12 minutes. When running, it makes a loud buzz such that you probably would want to be in another room. This is the voltage passing over the plates and converting oxygen in the air into ozone. After that, you leave the lid sealed for 2 hours so the ozone fully permeates your CPAP machine and kills all living bacteria and viruses by oxidation.
Some folks complained of a smell or brown discoloration of their mask after the first few uses but I never experienced either of those issues. I think the trick is to follow the instructions from SoClean: use the provided fragrance-free soap to thoroughly clean your mask and if feasible, use new tubes and generally clean your machine as best as possible prior to setting up your SoClean 2. You will get better results. If your machine is dirty and you run SoClean with it like that from the start, you may smell oxidation related to the ozone attacking residual bacteria or simply grime. I suspect that the discoloration issues might be related, too.
I've been very pleased with my SoClean 2 though as noted, I did without an automated sanitizer for many years so it's more of a luxury than anything else. Or maybe you can think of it as extra insurance, since it will run ozone all through the machine, tank, and hosing. Remember, though, using SoClean doesn't mean you never again wash your mask. You'll still want to do that periodically, if only to remove surface oils.