I have a 2012 Edge SEL w/ ecoboost that I bought in June of 2013. My wife and I kind of share it throughtout the week, her more city, me more highway so my mpg is also an average of that kind of driving. The lowest I've ever calculated was 20.9 mpg and the highest I've ever gotten was 31mpg, on average it looks like I am getting 23.3 mpg. I tend to drive it at 68 mph since I saw a post from another ecoboost owner who found that was the sweet spot for highway driving, at least for their car. I will say that most of my exclusive highway driving usually gets me 24.3 to 25.7 mpg, between my wife's city driving and how she actually drives the car is what really brings down my daily average.
Just be aware if I remember correctly I calculated that extra cost for ecoboost would take about 4-5 years to make up the difference compared to a normal midsize SUV. I plan to keep mine for longer than that so I was fine with that, plus I am getting about the same mpg as the 2000 Toyota Camry V6 I had. So I like the fact that my gas bill is basically the same instead of it going up if I bought a non-ecoboost version.