Well, blah is about the best I could describe the economy mode. After driving the performance tow mode for just the month or so that I did...it was literally unbearable to drive the economy mode again. I lasted 60 miles, pulled over and switched it back.
As for the actual results..

I set the tune for economy, reset the fuel mileage lie-o-meter, and off we went. MPG at 50mph was fantastic, 16mpg or so for about 10 miles. Got on the highway for 20 miles, averaged 15 mpg at 65 mph. Reset for in-town driving. MPG was about 11.5-12.5 for 35 mph and stop and go. Back on the highway at 70 mph, reset again, averaged 13.5-14 MPG. Then I pulled over and switched it back because it was like trying to drive a nutless wonder...it's no wonder I hated the stock shift and fuel strategies-they SUCK. If you gain nothing from reading this but one thing, know this, the truck in stock form is a limp piece of crap compared to running it with a tune from Mike at 5-star. There is only one thing I would change about Mikes performance tune-I want it to shift into 6th gear at 50-51 mph, it currently will not shift until 56-57mph, and that means it hardly ever hits 6th gear unless I am on the highway. I am more than willing to forgo the gas mileage to run the vehicle in the performance mode. Hope this helps, feel free to ask more specific questions if you have them.