I bought my car, a Toyota Prius Prime plug-in hybrid, on December 23rd. It took almost 188 days—more than six months—before I finally put gas in the thing.
Friday morning, on my way to Toronto, I put 34.8 L into the car after driving it 2183.6 km since the dealer delivered her. That's an average efficiency of 1.6 L/100 km, and an operating cost of 1.4¢/km.
For comparison, the last six months I owned my last car, she was getting 13.3 L/100 km and had an operating cost (because of maintenance as well as gas) of 52.9¢/km.
The whole trip to Toronto, during which the car ran almost exclusively on gas instead of battery, used only 73 L of fuel and averaged 4.3 L/100 km.
I think it was a good purchase.
Also, let me just say that adaptive cruise control makes long-distance drives a ton easier.