I get 28 mpg on ECO Pro. And about 18 mpg when driving hard on Sport. I can live with both.
I think the coolest thing about having driving modes is how it remedies the biggest problem of speed junkies. Getting used to it. Meaning no matter how many horsepower you have, or upgrade to, at some point you get used to it. But with the driving modes, I find every time I move from ECO Pro to Sport puts a smile on my face. I used to drive my wife's car for a few days when I get bored with mine, and it's always nice to get back in to my car. Driving modes give me this options with a click of a button. Love it! Btw. it's not going to stop me from modding though ;-)