The benefit and trouble with rotary engines is their reliability -- fewer moving parts means they'll generally fail less during their life cycle, and running them under higher loads / higher output, within their specifications, will generally not reduce the life expectancy (as in, run a 100HP rotary continually at 30 or 100, nearly the same running life).

But they will have a shorter overall lifespan. That large moving inner chamber and the outer chamber walls around it will wear down, and when they fail you replace a significant amount of that combustion chamber (or just junk the entire motor).

It's a neat application of the technology, and particularly in contexts where either the motor is going to run for long periods at a specific speed or not be used all the time, it could make a great option for power generation.