I have an '05 Prius, and my average MPG over the 39K miles life of the car is 48.7 mpg. I put nearly 38K miles on the car in one year, so for me this is meaninful. My VW Passat got about 24 MPG, so I am spending about 1/2 what I was for gas.
I have to confess, though, I got the Prius for other reasons, too. It has great gadgets. My favorite is the smart key system. I never have to take my key from my pocket to unlock the doors or start the car. It knows when I am there. The touch screen climate and stereo controls are cool. The regenerative braking system saves on brake pad wear. It's no race car, but I can cruise at 80 if I want, without strain on the car (I am 48 years old, so I don't do that much). There is plenty of room inside, as much as the Passat had.
But if you get a hybrid just for mileage, and you drive 12k miles per year or so, it doesn't really pay off.
Yeah, the smart key is fantastic. I figure I save about five hours a year not having to dig in my purse for the keys. I really like the car because it's so entertaining.