The reason that Volt hasn't sold isn't because it isn't a good idea, it's because the public isn't ready for it. Hell, there was a time when the public wasn't ready for an aluminum engine. GM sold it to British Layland back around 1964 and this "bastard step child" of GM went on to be used by them until just a couple of years ago in 2006ish! Maybe still, but I believe it isn't used at least in the Land Rover.
The public just can't grasp the idea of the electric, we will see with the Leaf, it may be what will grab hold. People see a number, I can drive 50 miles, lets see it's 20 miles to my friends house, 20+20 is 40, 40 is less than 50 so I can go to my friends house and back and charge it tonight. Maybe the public thinks like this and the Volt doesn't compute for some reason, I don't know but it makes perfect sense to me personally.