I would think that a lot would depend on the kind of driving you do and your definition of "worth."

For most looking at 'work-to-home' commuting the idea of charging your extra batteries for a quarter by plugging in at night might make the difference between a zillion miles per gallon and 50MPG. I've talked with several people that tell me they are waiting for a plug in hybrid ... believing that it offer the maximum versatility between great fuel economy/low emissions and the need for longer distance 'away from the plug' driving. It make sense to me ... a non-hybrid driver???

BTW ... great article.

--RichC --- "My Desultory Blog" & CinciTDI Club