I would not want an Eco-Boost engine past its factory warranty period!
I understand the trepidation since it only came out 3 years ago and the results are still coming in. That said, to date it's doing very well. My experience is excellent. The MPG are very good and the towing is leaps and bounds ahead of any other gasser I've used.
The only drawback I've experienced so far is the engine braking when you downshift on a grade, especially with a 7000# trailer. The little motor just doesn't slow it up.
Going up the hills is terrific and it pulls just as good or better than the early 2000+ 5.9L Cummins, even at low RPM's. Also, pulling I get around 10.5 mpg verses 7 mpg with my old 2002 Screw.
So far....very good. Time will tell. I pull the trailer ~15% of the time and I'll cross 100k in a week or so.