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.
It sounds like your friend installed or used his toilet incorrectly. There is a tight seal on the compost chamber. A fan creates negative pressure, so there is literally no way odor can escape into the boat. Even when sitting on the throne, the air is sucked into the bowl, away from the user. You don't even smell your own poop. There is less odor than the toilet at home. Your friend should call the dealer, and they can figure out what he has done wrong.
Now, there is some misunderstanding out there regarding how to deal with the solids. After the toilet is full (about 6 weeks for us), you'll need to store the solids somewhere else for another 12 weeks, for the composting process to fully complete.
This is what we have found works best, after years of experience. Take a compostable plastic bag (cheap from the hardware store) large enough to go over the lower solids bin. Invert the soilds bin and dump the contents into the compostable plastic bag. You don't need to clean out the toilet - left over material helps start the composting process again. Add peat moss and close the toilet. This is a fast job, and not unpleasant at all.
Then take the bag, and put it in a 5 gallon bucket (usually free from a restaurant). Leave the bag open, through some dirt on the top. Put the lid on the plastic bucket, and punch some small holes in the lid for ventilation. That's it. In 12 weeks, put it on plants. For a coastal cruiser this is about as easy as it gets. No pumpouts!
If we are on a long cruise, we can't take the material home. So, we try to visit a marine park where the solids can be safely and legally dumped into their pit toilet. In the event we can't find a place ashore to dump, we store the bucket in the lazarette until we can. This has always worked. It doesn't stink at all.
Obviously, when offshore you can dump over the side. Outside of the US, laws are much more logical. In most countries, it's 3 miles out to dump, and as far as "practical" in Canada and New Zealand. That means if you are in the deep channel between islands, you can dump it. US laws are zany when it comes to boating sewage.