We have a C-Head, our first loo in our homemade boat, and so far, in 9 months of light use, couldn't be more pleased. The simplicity of design, the ease of keeping it clean, the fact that its few parts can be easily, locally and cheaply replaced, make it excellent for our needs. We don't need to buy a big expensive custom jug for the urine, (just screw on the cap and put another clean gallon jug in its place. next time we go ashore, we take the full jug in a grocery sack, and empty it into a toilet, or dump it in the woods. It IS sterile, after all.)
At $500,it is hard to beat the price of the rig, and frankly, I don't care where the nearest pump out is, how much it costs, etc. When the fiber/poop mixture seems hard to turn, the contents are emptied into an ordinary 5-gallon bucket, which is ventilated, where further drying takes place. Composted? Not really, I suppose. but dried into an entirely odorless lumpy mix that can be tied up in a plastic bag and chucked, less offensively than cat litter or used Pampers. Or a permanent lid can be fastened on it, and chucked, and by the time THAT decomposes, the contents will be the least of our problems. As for me, I plan to start a long-term compost bin not too far from our dock, well hidden by azaleas, which should be happy to have it.
It is easy, needs no nasty chemicals, no emergency 'unauthorized-deposits'-caused tear-downs, and has, so far, no odor at all. No bugs, either. I may have to eat my words some hot summer day, but that day hasn't come yet.