Evac also makes systems for use on board (mainly cruise ships). My only concern at this point is the treatment plant. Their product seem to target much bigger ships but I'm sure the dealer will follow up on this issue soon.
One of the advantages of the EVAC toilets is they offer a special adapter to fit a bidet seat. More on bidet seat for existing toilets soon in another post. You won't believe the stuff they make these days to clean your rearend and particularly how they manage to make a very fine animimated movie about , well, taking a shit !
Vacuum systems allow you to save a lot of water, allow smaller piping and unlike traditional system, more installation flexibility like piping going upwards.