[DJL]

When it gets cold, battery power drops off, plus you need some sort of interior heater. Where does the interior heat come from? The batteries? When it's -20F outside on a January morning in Maine, those batteries will be lucky to move the car out of the driveway, never mind power a heater...

Or is this pretty much just a car intended for summer use?

 

[kubel]

The batteries will be temperature controlled: Cooled in summer, heated in winter.

The cabin will probably be heated by electric heaters and engine heat from the genset, along with better cabin insulation.

These are some of the issues GM is still ironing out.

 

[BigRedFed]

From one of the recent posts by Lyle on the blog, it appears that GM is planning to cut the engine on if it is too cold for the battery and won't use the battery until it is warm enough.

 

[ClaBerCla]

It takes about 1.5kwh to heat the cabin

Energy density in the batteries will be around 16 kwh. To heat the cabin (if it is well insulated), it should take less than 1.5 kwh. A 1500 watts heater will produce 1.5kwh during one hour.
So, the volt will run on electricity during 36 miles instead of 40 miles during the winter : 40*(16-1.5)/16