As much as I dislike GM (and believe me it is a lot) and would never buy their product, I think their approach with the Volt is correct.
Having only electric propulsion and using carbon fuels to carefully generate electricity with the engine running at its optimum efficiency makes a lot more sense than the more typical (and really complicated) hybrid drives. There is a reason that railways propel with electric drives and no transmissions. In addition to complexity, the need for torque and rising rpm's mean hybrid drives can't always keep the internal combustion engine at the most efficient operating loads.
I don't understand why the entire industry doesn't go this way.