For as far as I drive for work it is a must. I currently drive 65.7 miles one way to work. So that equals 131.4 miles a day.
Thankfully I have a job that allows me to work 7 days on 7 days off. When we first moved to our new house I was driving a 1992 Nissan pickup. It was getting 26 miles to the gallon, not bad but it was costing me almost $330 a month
Currently I have a 2007 Toyota Prius it averages 50 miles per gallon. Now with gas over $3 a gallon again it is only costing me $140 a month to go to work.
This is my best tank seance I bought my car a little over a year ago. 
53.1 miles per gallon and 358 miles total was on the tank, with a quarter tank left when I filled up.
It truely has been an amazing car for us!
Living so far away from the city, or even the town we live in. Makes it much easier and less stressful about trips to town. It holds quite a bit too, the trunk is large!