I think the best hybrid car is a diesel mommy van in the garage with an electric battery powered econobox commuter car at the curb. The combination costs twice as much as a van or an econobox, but it gives unrivaled range/capacity and high gas milage.
Take the van if you need capacity or range, take the battery powered econobox if you want high milage. Since you use each of them half as much they will both last twice as long, and you don't have to compromise on design.
I've used the two-vehicle solution for years, one small commuter and one larger but rarely used.  Alas some real-world issues spoil it.  For one, I have to pay double in insurance premiums, and since I don't drive a lot, I pay more in insurance than fuel.  (And presumably the insurance execs use the proceeds to burn some fuel somewhere.)  Also, here in Vermont, with salt on the roads all winter, cars rust out after some years, so I generally end up throwing a perfectly good engine away (with its embedded energy content).  These are just two examples how our society is set up in a way that makes it hard to do the right thing.  E.g., if we all stayed home when it snows, and skipped the salt, we'd have a happier life and our cars will last longer.  But no, the motoring religion says: we must be able to drive to Wal-Mart at any time!  And we must keep the roads "safe" for that.  Never mind that despite the salt there are LOTS of accidents during snowstorms.  Anyway, the main reason I keep two cars is so I can drive the small one most of the time and set a good example.  (That's when I don't ride one of my several bicycles.   Loved the quote I saw on a TOD page recently: "Every time I see an adult on a bicycle, I no longer despair for the future of the human race." —H. G. Wells, 1904)
My wife and I have adopted this approach.  We recently  purchased a 1991 GM Metro (40 mpg/city). We still own a 1995 Ford Ranger p/u, but now rarely drive it.  Both of us walk to work, so our mileage is quite low.  And it is quite shocking to drive any distance in the traffic prevalent in our area (Sacramento, California).  People are so stressed on the roads and many drive like complete maniacs.
I have thought a lot about this sort of thing, since if I were honest, I would shut myself down pretty soon since I can't twist my neck much anymore and am getting almost as slow as the nuts I have to dodge when I go into town in my little dirt road.  What seems to me is the right solution is the car club, in which everybody has access to any car they might want at any time via cell phone, so a central computer knows everything necessary, and if I want to go , I just hit the button and bingo! a car of the right kind (econobug, bus, rusty pickup, muscle rocket, etc) shows up and takes me, or lets me take it.

This way, I pay just for what I use, and somebody else more competent is doing the nightdriving, fixing the flat battery, the headlight, the skizzy computer and all that.   I had a student who did a great job simulating this, and what he showed was an amazing saving in everything- money, parking space, total time devoted to transport, home space utilization, and the works. Average time delay was 7 minutes.  So? You call ahead of need.

By the way, I tried to sell this idea locally (many times) and the people who like it the most are young mothers and Quakers, and the ones who call me a commie trying to rob them of their hash and sex are young men.