I'm all for a diesel hybrid too. A 1.5l 3-cylinder diesel could easily produce 100 hp on its own and add whatever electric to that for quite good performance. With a slightly diminutive Golf-like platform it would easily get 75 mpg in the city and 50 on the highway.
I would recommend reading the "Dashboard Hybrid Sales" report (Google it) because it includes hybrids, EV/plug-in, and diesel sales. So for February 2011, the numbers were:
23,263 (+19.5% vs Jan. 2011)
By focusing only on Otto vs Diesel cycle efficiency, diesel advocates often ignore: engine overhead and Atkinson efficiency. It turns out that four cylinder gas and diesel engines burn fuel at just about the same calorie rate when stopped. But then the hybrid cheats and 'shuts off' automatically and starts up when the gas is pressed while the diesel continued to burn fuel at the stop light. Furthermore, the 14 to 1 Atkinson expansion ratio and 8 to one compression ratio gives diesel-like efficiency in all but the highest, hill-climbing and pedal-to-metal accelerations. - Bob Wilson HSV AL.
Both Hybrids and super efficient diesels are stop-gap technologies. Even a diesel-electric hybrid would be the same. If we are running out of petroleum fuels, eventually neither will be a solution. Still, stop-gaps can help extend the time we have left.
Given the choice, I'd buy the efficient diesel. It just seems wasteful to purchase a vehicle with two power plants when a single-power vehicle with the same fuel mileage is available.
I never liked the hybrid nature of hybrids. Messy, heavy, expensive, dual powerplants involved. I'd prefer an efficient diesel any day.
But even better than that, I'm aching to see fuel cells, fed by something that separates the H2 out of fuel right in the car, and an all-electric powertrain. Heat pump for heating and cooling of the cabin. Can use biofuels or existing fuels, and certainly the existing fuel distribution systems. Should be at least twice as efficient as internal combustion engines. And if mated to a hybrid-car-sized battery, it could beat the pants of hybrid cars in terms of fuel economy and simpler mechanical components.