Some good points raised in this thread both sides of the argument.
Here are some more to throw into the mix;
There is a good reason why most commercial vehicles and semis are diesel.
The additional capital cost of a diesel is regained in the trade in value, not sure about here but in Europe where 25% of cars on the road are diesel, diesels devalue far less than gas cars. There is a higher demand for used diesels.
I bought a 2006 Honda CRV 2.2 TD (Europe) and it had better (published)emissions than its 2.0ltr gas counterpart.
Diesel is a much safer fuel, in a car wreck, in canisters, being transported, whilst refueling and of course on boats.
I am glad my Honda S2000 is gas and not diesel though.
Having said that, see this: Audi's diesel race car too fast for its own good