We've had a SaniCon unit for over ten years. When we bought our new coach last year, it was the first thing I added. I also think the sewer solution is a good alternative, but with the west coast drought, it's hard on water usage.
The SaniCon really doesn't need any water to rinse. If I think I need to rinse and don't want to use or waste water, I just close my grey valve the night before we leave. The next day I dump the black, open the grey, let the two equalize, close the grey and dump the black. I do this twice which gives the black tank a nice soapy rinsing. No additional water. Required.