We had a composter on our boat and it was a great solution...but we would never consider on for the RV. With a boat you have to find a functioning pump out station if you want to stay legal in most areas but they always seem to be broken...then it's about a 1/2hr job...so the composter is just more convienent.
If you are traveling at all, it's just too easy to swing by the dump station, 5 min to hook up the hose and pull the valves. Even if you aren't pick up a blue boy and strap it to the back of the RV.
I've used a casset toilet a few times, another no thanks...the size is drastically smaller so you have remove it and carry it to a dump station daily.