I've got decent willpower, and with a torque-beast V8 I'd have no difficulty keeping RPM down...that's exactly what I enjoy.
If my priority was winning a fuel economy competition, I'd get a VX. If my priority was TCO, I'd get a $300 Neon, Escort, or Cavalier...and/or a scooter/motorcycle.
My priorities are more varied and vague. My first priorities are comfort, affordability, and manual transmission. Next is a minimum standard for image. Then there are practicality, fun, and
interesting image.
Comfort: If I'm not comfortable I won't drive efficiently, and with the amount of time I spend driving I'd spend a significant portion of my life feeling miserable. I drove an uncomfortable car for over 150,000 miles and I'll never do it again. Comfort for me isn't the same as comfort for others; I need armrests in certain places, leg positions that are just right for me, and a decently smooth ride.
Affordability: This can vary based on value and my own financial situation. It does not mean the cheapest car around! It is based mainly on TCO, but my TCO calculations may differ from someone else's.
Manual transmission: I don't want to buy another car without one. Important to me for my enjoyment of driving as well as hypermiling ability.
Minimum standard for image: I need to maintain a professional image and fit in with the normal people. I can't drive a rusty jalopy or a riced out car to work every day, and some day I'll need to interview for a new job; I must drive something respectable to interviews. I guess for interviews I could borrow someone else's car if mine wasn't respectable.
Practicality: This one is pretty easy. Me, my wife, her purse, and my backpack are all I need to carry in my daily driver. More practicality is a bonus.
Fun: RWD is a HUGE bonus here...I like to kick the rear out around the occasional corner. Handling is important: I don't have fun with understeer; I don't mind if it handles slowly but evenly. I love my VW's handling.
Interesting image: I have zero interest in other people thinking my car looks cool. In fact, that's a detriment to me; I dislike attention. I do like a car that interests my eyes as I walk up to it, though.
The C4 meets some of those standards, I'm not sure on others, and goes against a few. Its individuality strongly interests me; I really enjoy the idea of hypermiling something that nobody else hypermiles.
Oh, and my current VW Rabbit? My priorities were a little different; at the time, I
needed a brand new car that I could be 100% sure wouldn't cause me any difficulties. It delivered that, not needing repair until it was well over a year old and that priority didn't exist anymore.