I owned one – a 2007 2.7HDI model for over two years. Great car very unique and very beautiful! Very special and a dreamy comfortable wafting drive. Lots of gadgets – heads up display, swivelling front lights, reclining heated rear seats (if you get a lounge pack), etc. It was designed for the French president so it’s got that luxury limo feel in a quirky French way.
Negatives are things break and can be costly to fix which was ultimately why I sold it. I was sad to see it go though. Have a look at the C6 owners website for more info about typical C6 issues – it’s a great resource. When everything is working it is one of the coolest cars to cruise around in I reckon.