I think I achieved the record low mileage with very short commutes and pre-heating the cab when it was 30 degrees below zero here in Fargo in January and February, of 29 mpg. A few people, with good conditions, are coming in very close to those EPA figures. Consumer Reports said 44 mpg city/hwy average.
Basically, the first five minutes of driving, as the engine warms up in Phase I of its program, are likely to be 25 to 30 mpg. After that, the sky's the limit, depending on your driving conditions, ambient temperature, and driving style.
People are also reporting dramatic improvements in mileage after the car is well broken-in at a few thousand miles.