My 2005 Civic Hybrid has already paid for itself. By that, I mean that the additional cost of buying the hybrid vs. a similarly equipped Civic has already been recouped - sort of. By "sort of", I mean that according to the Kelley Blue Book value, my hybrid is worth $1600 more than a similarly equipped non-hybrid. Add that to the $400 I got back from Uncle Sam, and the approximately $400 less in gas that we've paid (based on actual driving mpg and about 18k miles, ymmv), and we've passed the approximately $2200 extra we paid for the privilege of owning a hybrid. Accuse me of contributing to the "smug" content in the air if you must, but I'll admit to being pleased with myself.
Just for the record, the decision was not made primarily for financial reasons, so the fact that it has already "paid off" is just icing on the cake.
For those wondering why I bought the Civic Hybrid (as opposed to the Prius, for example), it really had to do with my familiarity and satisfaction with the Civic. Our last car was a 1995 Civic that had about 140k miles on her (IIRC), and had at least another 140k miles in her if she hadn't been hit by a semi. Yes, I was driving at the time - at approximately 70 mph. For those who think bigger cars are safer, I suspect that in this case I would have been far more likely to have been injured if I had been in an SUV, for example. As it was, my wife and I walked away (or were towed away) without a scratch on us. That strongly contributed to us buying another Civic.