We had one in our boat and loved it...but in would never consider it in the RV.
In the boat, you generally can't dump overboard and finding pump outs is a hassle (plus they are broken half the time). Marine toilets require substantial maintenance as they pump the waste through 1.5" pipes and tend to clog and require regular rebuilds.
On the RV, it's just not as big of an issue as they use gravity and large diameter pipes. About the only reason you might consider one is if you are in the back-country for long periods of time with no access to a dump station. You still need a place to dispose of the urine every couple days but the solids should be good for around 3-5weeks.
One catch, our experience is with 2 people using it. If you have 4-5 people, it becomes problematic as they can't handle the loading (from people we know who had visitors for a week on their boat with the same unit)