This comment also made me wonder about the cold-weather usefulness of this sort of device. As I write this, it's -20C outside in the middle of the day. Granted, this sort of weather isn't a problem for much of the world but it's quite common here and affects a nontrivial number of people.
The "inefficiency" of a IC engine gets put to some use in that some the "waste" heat is used to heat the inside of the car, and you don't really get that benefit in an electric car (and any hybrid I've been in ran the combustion engine constantly while the heater was on). This problem has existed in the past with air-cooled engines (old Volkswagens come to mind). At the time, it was common to have a separate heater that burned whatever fuel the vehicle ran on. I'm thinking that the same wouldn't work too well on an electric car -- running an electric heater would probably put a really big dent in your range, and it would be a real bummer to freeze to death on the side of the highway because your car's heater killed the "battery". This would be a problem with any sort of electric car, but probably not an insurmountable one.
Probably more serious than that, though, might be the impact on the function of the engine itself. Most IC engines will run fine in cold weather assuming you can get them started. A common problem is that the car's battery (particularly older ones) can't deliver enough power at low temperature to turn the engine. I am a long way from an expert in the effects of temperature on various battery chemistries, and even less of one on how low temperature would impact the capacitor-like devices described in the article. I do know that it would be a fairly serious end-user problem if your car just wouldn't work on a cold day.
Does anyone have any insight into the temperature sensitivity of this kind of scheme, and how it would stack up versus comparable battery-based technologies?
It sounds like a promising idea, but it would be a non-starter in many places if it doesn't perform well in very cold (or very hot) weather.