I have a one-year-old SE Sport Hatch with the manual trans and grille shutters. I run 40 psi in the tires and 0w-20 synthetic oil. Since new it has averaged 35.5 mpg. The bulk of the miles are accumulated in my 20 mile each way commute (14 mi highway, 6 mi city). As others have noted, I loose about 3 mpg in winter driving. I have also noticed that the wind is a big factor. I can easily loose 3 to 5 mpg with a strong headwind or crosswind.
On longer trips that I have taken, the mileage is nothing short of phenomenal. The Focus easily gets 42 mpg. This is a two way average with the cruise set at 70, the AC on and running 87 octane fuel with ethanol.
Vinnie