We put on a Nature's Way a few years ago, and are generally very pleased with it. It sure beats having to worry about overboard discharge in places that can't handle it or shouldn't have to handle it. In fairness, if used daily for several weeks in a row it can get to where it needs a break. So when we're in a marina (which we are quite frequently over here) we generally use the shoreside facilities. For situations where you're mostly going cruising on weekends, with the occasional 2 week cruise, composting heads are almost ideal. The frequent break between usage gives it a chance to compost, and you end up with a loam mixture that you don't mind tossing in the woods outside your back yard. A couple could probably go the whole summer and not worry about changing out the peat until the end of the season.
There's a bit of an art to it, and it takes getting used to, but we're very pleased with it. We gained a lot of space where the holding tank and associated pipe used to be.