Well - when the time to buy comes round again:
I'm a retired en-ga-neer and have 'sucker for tech toys' written all over me.
Unfortunately I'm also in Soy Bean Diesel country - may have to consider one of each - and then we also have ethanol/gas blends at the pump.
heh heh heh - decisions, decisions,
It's an area that is moving so fast.
When the hybrid diesel-electric plug in comes in, it will not only be a mouthful of a car (PDHEV or PBDHEV), it will get 80mpg+. However it will cost more (diesels cost more, hybrids cost more).
I'm a big fan of minimising new technology risk (son of an engineer-- you don't reinvent the wheel when 10,000 people might die on your mistake). I let other people do the Beta-testing for me: I'll upgrade to Windows VISTA in a year or so's time, when I am forced to, not before.
So a hybrid now, yes, because there is now 7-8 years of experience in Japan in driving these things. Diesels are widespread in Europe, half of new cars, the problem will be which diesel cars will come to the USA? The best car makers (Toyota, Honda) are much less gung ho about diesels than the European manufacturers, who have higher cost of ownership and worse reliability in their brands.
The irony is the US domestic manufacturers all sell excellent diesel cars in Europe, but those cars by and large cannot be bought in the US. I think GM is marketing the Opel Astra (Vauxhall) as a Saturn. They also don't tend to be too badly built (but they don't match the Japanese).
Although VW Golfs are great cars to drive, they can't match a Honda Civic or Toyota Corolla for reliability and cost of ownership. Don't talk to me about Mercedes! BMWs just cost, even over here, to fix. My brother's Volvo (8 years old) is just out of extended warranty and is costing him a bomb (he probably does about 10k miles a year, in the Canadian winter and summer).
Plug in hybrids will be spectacular vehicles, but the battery life issues are not resolved.
So my own feel, on this side of the drink, is I would buy a diesel (hybrids are really a premium product here). On your side, I would try to wait until the 2009-10 model year, and see what was on offer, diesel v. hybrid.
Ethanol I think is a political and environmental con (this is not the case with sugar cane ethanol ie Brasilian or Cuban, but it is with corn ethanol). It's success is more about Iowa being a key presidential caucus state than about any practical advantage to the US or the environment in growing it. The subsidies are just going to waste.
The president was irresponsible to future generations of Americans to advocate ethanol-based fuel over more efficient cars (he was aided and abetted by senators and congressmen from both sides of the aisle).
Bio-diesel is a good fuel, especially as soybeans are a 'nitrogen fixation' crop and far less damaging to the soil than corn and all the chemicals that go with maize-growing (you can see the fertilizer bloom on pictures from space, a giant patch of dead water in the Gulf of Mexico, from all the fertilizer washed down the Mississippi).
Bio-diesel made with palm oil imported from places where they destroy tropical rainforest to build plantations (Indonesia, Malaysia, Paraguay etc.) is the ultimate environmental disaster, and should be banned.