I have considered using a rotary very seriously. About four years ago I bought an RX 7 and overhauled the engine to learn more about it. It was dead simple to work on compared to a piston engine. I sold the car about a month ago after driving it about 25 thousand miles with no problem. No problem except keeping the gas tank full, it never got more than 24 miles per gallon, and usualy about 20 around town.
I've decided against using a rotary for the following reasons:
1. The mechanics of the engine are very simple but the systems necessary to use it in an aircraft are not. Cooling, induction, ignition and exhaust are all systems that would need to be developed for a particular installation. It seems that someone has done each of them well but very few have them all well done in a flying aircraft. Something as simple as a muffler isn't simple on a rotary. Add a PSRU, even a good one like that of Tracy Crook, and it seems to me you have negated the value of mechanical simplicity compared to a Lycoming.
2. Most don't seem to produce the horsepower they are expecting. The nature of the rotary requires that the induction and exhaust system be tuned to narrow limits to get the performance the engine is capable of. I'm not aware of off the shelf products that provide that and I'm not interested in spending a couple of years trying to develop them myself.
3. It would take a lot longer to build and tweek the rotary to a usable level, probably cost as much as a used Lyc with 1500 hours on it and even longer (and more money) to feel comfortable going over the horizon. That's not where I want to spend my time or money. With the Lyc I have 500 hours before overhaul (if I want to do it at TBO) which will last me about 7 years. In that time I can save for the overhaul and enjoy a lot of flying.
I could go on. I'm sure there are those who will argue with each of my observations, but for me the Lycoming is the better choice. I'm currently flying my second project, a Wittman Tailwind with an O-360. It had 1300 hours on it when I bought it ($6000.) so I considered it 'well proven'. Add gas, a little oil now and then and fly, its that simple. With any luck it'll still have a few hours left when I finish the Cozy. Works for me.
Mike