I had the opportunity to see a composting head that a friend installed on his boat. He removed it two days after I saw it, pretty much echoing Chris' statements. There was a definite, pungent odor on the boat, but I guess if you lived with it daily, your olfactory senses would eventually block it out. Kinda' like entering a home where they owners have a couple dogs and cats - the place smells like a kennel, but the owners don't seem to notice.
As for the sanitation issue, I think this is where common sense must come into play. Those turds contain a large quantity of fecal coli-form bacteria. The definitive test would be to wipe the seat lid, inside and outside, with a sterile swab, then place the samples in an appropriate media in a petri dish. That would be the definitive test of this device.
For me, I'll stick with pumpouts when I'm inshore, and direct discharge when beyond the 12 mile limit. Oh, I asked a sheriff's deputy about peeing over the side. He said he doesn't know of any law in Florida that prohibits it, other than public nudity. He also said laws in other states may address this, but he didn't know for sure.