I have a prius and though these cars do have reasonable gallon/mile of roughly 40 mpg, (the new ones are up to 45 mpg), there is reduction of pollutants out of the tailpipe. These type of cars are not the solution to the pollution and use of finite resources problems.
It now is down to about $3000 to replace the battery (I have 125,000 miles on my battery) which is a lot less then a new car. I do like the electric motor torque for get up and go...
The seats really suck for any long distance drives on these cars, and the GPS/Stereo/Blue tooth/car status readouts is very nice...
I have found a new hybrid - me - I plan to start riding my bike to school this summer which might take off my spare tire and reduce my fuel footprint (it is about 19 miles here and there and back again)...