Too bad the OP hasn't been able to get any real input on his question ..... There seems to be a LOT of resistance to the use of composting toilets .... Some of it for good reason and a lot of mere superstition.
I guess that is the answer....Not too many people using these things because most everybody else will think you are crazy.
Bill001 .....If you decide to go with one of these I would be interested in how it goes ..... You can PM me if you don't want to put up with all the flak.