If you drive around Atlanta, you see a lot of Nissan Leafs (Leaves?) around this place.
The Leaf is really the first truly usable purely electric car. Unlike the Chevy Volt, which uses a gas engine as a range extended to keep its electric powertrain running, and the Toyota Prius, which uses the battery really to take over tasks from the gas engine and extend range (i.e. mileage), the Leaf relies solely on it batteries for locomotion.
Unlike the Volt, it has roughly an 80 mile range before requiring a recharge (the Volt is good for 37).
They're kind of 2 sides of the same coin. The Volt can be taken on a trip of some length, because it's gas engine will power an electric motor to continue to run the car. You get about 400 miles before it's time to refill. GM says this makes it the equivalent of a 37MPG car in this type of driving.
I will point out that nearly all turbo diesels sold by VW and Audi beat this easily, pushing 45-50MPG in highway driving. So, if you're interested in highway efficiency, with the Prius hybrid (which pushes 50MPG) or a TDI is a more efficient choice.
If all you're doing is local driving, and you can suffer the 4-8 hour recharges required on these things using normal household current, then most people estimate you're looking at about $2 worth of electricity to restore to full charge. Until gas/diesel is back at $2/gallon prices, that makes the plug-ins more efficient, but, you need to understand the other trade-offs with these, which include the dwell time while they charge, the loss of efficiency in the summer months, and the ultimate super charge when you replace your batteries at $8000 after 6-8 years.
Top that off with the still real risk from fire with Lithium Ion batteries (google Chevy Volt fires and check out the 787 Dreamliner's problems with this same technology), and I still think people are buying these for vanity reasons, and not because they're either better cars, or even more fuel efficient over the long haul.
As for me, I did choose a TDI, and I got a car I know will give me 38-50 MPG consistently, and will not require an engine replacement at the 100-150k mile mark.