A large part of the problem with EVs is that current technology limits their range. To really get the most out of an EV, you have to not drive all that much to begin with. However, if you're not driving that much, you're also not buying that much gas. Even if you completely eliminate your entire gasoline bill, the total amount of money you're saving isn't that much.
One local news station recently ran a story about a dealership rolling out the first all-electric vehicle in the area, the Mitsu i-MiEV. The car costs $29,000 and has a range of 68 miles. If you were to drive the full 68 miles every day for a year (24,820 miles) in a 30mpg car, you'd use 827 1/3 gallons of gasoline, which is $3,309.33 at $4/gal. You'd be saving $16,546.67 over 5 years. A 40mpg car would drop the savings to $12,410. If you're not willing to push the limits of your battery capacity and play it safe at 50 miles daily (18,250 miles), you're only saving $12,166.67 or $9,125 over the gas cars. There are a lot of variables that come into play, but you may not end up saving all that much compared to the extra cost of the car (the 38mpg Smart coupe starts at $12,500).
However, the dealership itself says that the car isn't meant to be your sole vehicle. It's meant for known-distance commutes and quick trips to the store. Figure in the cost of a second car, even if it's just a beater or a rental, if you ever want to go more than 68 miles without stopping to recharge it. Plus, it's an ugly little 4-door Smart-looking thing. To quote my girlfriend when I opened the page, "What is that? It's horrible!"
There's no way I could get by with just an i-MiEV. However, a Volt would work out very well for me. I commute about 20 miles a day, and the nearest city with a mall and public transit is about 20 miles away. I wouldn't feel safe with a range of only 68 miles, but most of my driving in the Volt would be electric. Even compared to my 25/37mpg Cobalt, I figure the Volt (including electricity costs and some gas for longer trips) would cost me about $500 a year, rather than the $2,000 I spent last year. The 35/40mpg Volt is obviously much more economical if you never have to get into the gasoline, but the option is there if a longer trip suddenly comes up (e.g. having to drive to a remote site for work).
Despite being pretty much the ideal candidate for the Volt, I'm not sure if I'd ever actually make up the difference in price (after the tax credit). Though there are Priuses that have been running on the same batteries for over 10 years now, I'm still a little wary of the new technology (on top of being a new model). The styling isn't my first choice, but it's not terrible either. It's definitely not in the same class as my cheap base model Cobalt and I like the geek factor of the Volt. If gas prices go up significantly, the Volt would save me even more compared to the Cobalt. Regardless of savings or greenness, I don't mind the idea of lowering oil dependency. I'd feel a little more comfortable with a second gen Volt, but I'm hoping that they continue to flop and they go on clearance so I can snag one cheap (a few people managed to get brand new GMC Syclones for about 1/3 off when dealerships were trying to dump them). I also wouldn't mind seeing a (bio-)diesel option instead of gasoline for the ICE.
I really like the idea of using battery power for average commuting and such, but having nearly infinite range thanks to the gasoline engine if needed. Until battery rechargers are as plentiful and quick as gas stations, I think the Volt's hybrid setup is much more practical.