We just bought a new to us 2013 SuperCrew XLT (9,000 miles) with the Ecoboost. We've literally had it only a few days, did a test outing to a local CG earlier this week and it towed our 6,200 lbs (estimate) travel trailer with no issues. Being a mile high most of the time (pun intended) and sometimes going to 10-11,000 feet I think we will appreciate the turbo vs. naturally aspirated engine.
Our previous TV was 2007 GMC Yukon Denali XL and although so far it seems as the F-150 matches it with towing power, I do miss the smoother ride of the Denali auto-ride. The F-150 seems a bit bouncy, not sure if there are some remedies for that?
So far so good, looking forward to some more extended towing this fall.