Like I said, I have driven a Volt. I estimate I have just over 100 miles in one.
It isn't a designed car, it is a converted existing model. The body was not altered in anyway, except it has less ground clearance due to the batteries and their weight - gotta watch some of the driveway approaches.
Considering the actual purchase price that a consumer pays for the vehicle it is viable if you live in an area where it matches your commute. Our problem out here in fly over land is that we have commutes that are too long, and you rely on the gasoline engine for too many miles a day. The down side to making it cost effective is that it relies on tax credits - money from everyone else, to subsidize the cost.
I have driven it in weather near zero, and it was only for 20 miles, so I didn't notice the lack of a high output heater. I don't think that would be an issue in daily commutes if you lived in a metro area. At the dealership the jury is still out on how sub-zero temps would affect drivability, but I will tell you that 0-60 is snappy, passing is snappy, and 0-100 is less than 3/4 mile. This car flies!
We did some math in the office, and payback off the final price is not really too bad. If the batteries last as projected it is no more expensive to use than the Cruize (its body and running gear donor).
I wish that they would have spent a couple hundred of the high price and incorporated solar panels in the flat surfaces.