Gas Vs Diesel

Gasoline appears to have lost its biggest advantage over diesel in the US--Price.  Diesel is no longer the red-headed step child of fuel options here.  It used to be the fuel was more expensive, the engines were smelly and cost more too.  Now the engines cost more but are so much more efficient that the cost differences can be made up in fairly short order.  VW has a new TDI for the Golf that gets 65MPG with 89HP.  Apply some basic hypermiling techniques and you have a car getting 80+MPG with little effort (I hypermile whenever possible and routinely see numbers 20% higher than EPA estimates--get one of the competitive hypermilers in this car and I wouldn't be surprised to see 100MPG).

The smell issue has been conquered too in the latest generations of diesels.  Particulate filters in the exhaust system capture the worst pollution, improved combustion techniques minimize pollution levels in the first place.

Diesel also appears to be better suited to bio-fuels.  Conversion of used cooking oil and the like to diesel has become so common place there are commercial DIY kits for the process.