I've been involved with several military diesel hybrid vehicles over the past 10 years. The performance & efficiency offered for these extreme operating conditions is significant, especially when all the mechanical clap-trap is replaced with in-hub electric wheel motors.
It is true that hybrids are interim solutions but the point that has been missed is that this interim solution is a critical next step in the implementation of fuel-cell based prime movers.
I don't know how many more years will be required to make a fuel cell prime mover practical in passenger cars, but when they are available, it will be relatively simple to replace the CI ICE/ICE with the fuel cell.
The most efficient engines in the world are all turbo-diesels. Although Atkinson-cycle gasoline engines can be nearly as efficient, this is true only in a relatively narrow "sweet spot" of operating conditions (which the hybrid system can optimize), while turbo-diesels are much more forgiving (not needing a hybrid as much...which allows simplicity and lower cost). see: http://autospeed.com/cms/title_Brake-Specific-Fuel-Consumption/A_110216/article.html and http://ecomodder.com/wiki/index.php/Brake_Specific_Fuel_Consumption_(BSFC)_Maps
Also, another "pet point" I'd like to make: Everyone always assumes that EV's are the end-game, yet they remain very far from practical for most people. With today's power grid sources, you are just trading one fossil fuel for another (oil vs. coal+natural gas). Net energy efficiency is no better than a conventional hybrid or turbo-diesel. Maybe in 30+ years the grid will be powered by primarily green sources. The best long-term solution (IMO)is to leave the cars alone, and focus further upstream by creating biofuels or solar synthesized fuels. see: http://cyber.mpnodes.info/archives/67 and http://www.sapphireenergy.com/green-crude/ then, we can keep the existing infastructure (gas stations, etc.) yet be zero-fossil-fuel, zero-net-CO2, etc. Cheers!
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.
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.
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.
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)
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.