CGDA is the Magma tuning, who are one of my favorite bands. Their bassist, Jannick Top, definitely got into CGDA whilst in Magma, though it is hard to tell when and where. I understand he got 'down there' in increments, starting with drop D. I think their other monster bassist, Bernard Paganotti, also got into this tuning. There are some thundering low notes on the Kohntarkosz album which I think came from down tuning. I love the song De Futura on Udu Wudu, which I think definitely gets down to a low C on some parts.
I've tried CGDA. I think I would need a properly set up bass set aside purely for this tuning. I don't know if a heavy 4-string set would do the job, or if a 5-string set is in order. Dropping a conventional E down to C makes it floppy, but tuning a heavy-set G up to A would make it unbelievably stiff. I guess there is a compromise in there.
Naturally this tuning makes sense to me. I play the mandolin on the side, and I grew up playing the violin and viola. The viola barks out in CGDA tuning. What I find with this tuning is that it kicks blues progressions into the weeds. If you want to play those sorts of things you end up with your left hand heading back towards the nut rather than heading up the neck, and there is usually one note still 'on' the string you are mentally preparing to leap off and onto the next. This is good for destroying conventions and opening up alternative voicings. Suddenly you can drop 9ths into your voicings without wrenching your pinkie out of the socket, for example. Suddenly you can comp along an octave lower than you thought possible.... all good fun, but I think it would take serious work for me to become fluent in this tuning.