Pat and I have just hired a car in the UK for 10 days: a Peugeot 308, a proper 4-seater with a non-trivial boot and a turbo-diesel engine, generally a nice car. The onboard computer told us the fuel consumption, for a mixed cycle of town, country and motorway driving, was 54 Imperial mpg, or 45 US mpg. It hadn't been zeroed between hires, so the value covered 2000 miles. Not bad; and comparable to what you can expect from a Toyota Prius hybrid. Peugeot, along with other European carmakers, are working on diesel hybrids: they promise 83 Imperial mpg for the comparable model due in 2010, or 69 US mpg.
The main thought this experience has triggered is the insight that miles per gallon is now an obsolete and misleading measure.
What we should worry about is carbon emissions: grams per kilometre (or mile). For traditional cars, mpg is a perfectly good proxy. But not for hybrids. Once you enable recharging the battery from the mains, a car is no longer an isolated system. A hybrid used as an urban runabout in pure electric mode could have an infinite mpg; but it has positive carbon emissions, because electricity isn't carbon-neutral.
I think the author is definitely on to something, but even more, why is it that cars in Europe have so much better average mileage than cars for sale in the US? Must be the Socialism, I guess.