I recently saw some marketing material, presumably the sort that has been used to persuade my very own government of the value of electric cars. I seem to recall that it suggested there is a payoff in favour of electric cars if you assume that the regular sort get about 35-40mpg at best.
(Let me at this point say I'm a total amateur in this area, so treat my comments accordingly)
I drive an unmodified 2005 Peugeot 307 HDI Sport. I'm one of these nerds that actually knows what mileage I get, and keeps a close eye on it. I get 54mpg in the city, and at least 63mpg out of town - yes, it beats a Prius by a substantial margin in both environments :-)
Not that I don't like the idea of electric transport - I do, and I'd love an electric car and matching aeroplane. I just think the hype is a bit ahead of reality at the moment.