Gene,
An acquaintance has a Comanche 400. He, and others I've spoken who have flown them, love them.
The airplane was developed because Pug Piper was of the opinion that turbocharging would never work for a general aviation airplane, so the only answer was to start with a huge engine and the airplane could fly high and fast.
Initially, the engine had some starting issues and other niggling problems. Plus, turbocharging worked, so there were not a lot of 400s built. The problems got ironed out, so now they are machines that keep their value - but they do go through fuel.
Warmest regards,
Rick
