I bought a Valterra Sewer Solution last year (or maybe the year before - I dunno) so I could dump and pump waste into my city sewer clean out at home. It uses a nozzle and water pressure from your garden hose to macerate the waste. It also has a spray/backflush feature where you can turn the nozzle to that it is aimed back into the dump pipe. The first time I used it, I was amazed (and disgusted at the same time) at how much stuff I was able to rinse out after a gravity-only dump followed by a grey dump. So I use it a couple of times a year now.
I've never had an issue with clogs, but I just feel better about getting the big chunks out. And there were lots left behind after a "regular" dump. It has to help with smells (though I haven't had an issue there either).
