What timing... I take delivery of my first hybrid today, a 2012 Toyota Prius. I did some basic math in making my decision, so I'll share:
This vehicle will replace a 2005 Chevy Uplander that we drove an average of 27,500 miles per year. The Uplander is getting 17.9 MPG at this point (according to the onboard computer), consuming 1,536 gallons of fuel annually. At the current price of $3.95 per gallon in my area, it costs $6,068 per year in just fuel (87 octane). Running the numbers again for the Prius, and assuming 45MPG, fuel will cost $2,413 per year... a savings of $3,655 annually, or $304 per month. Even after my wife added all the bells and whistles and extended warranty (she did that while I was out of the room), we will only be seeing a net outlay of $170 per month. And when my 13-year-old son goes to college, he will take this vehicle with him.
The Prius owners that I know are extremely satisfied, and one has had his since 2003. Although there are many other factors to consider, my monthly budget is certainly a major factor. I'm viewing this purchase this way: I'm buying a new car for $170 per month.