They are awesome trucks! I love mine. Tons of power, good mileage, trouble free so far, and very comfortable. Is the one you looked at new? As has been stated, in 2015 the turbo, and exhaust brake were improved. The 6.7 has proven to be exceptional. Major repairs to this engine have been rare, with the possible exception of the job 1 2011's. Cab off repairs? Meh, not a big deal any more. Ford shops are set up for it, the truck is designed to acomidate it, and the techs are trained. It was (Is), much more common on the previous generation of Navistar engines trucks. If your the type of person that likes to not have to worry, then an extended warranty, and MBI are your friends.
I know the other brands make good trucks as well, so if your so inclined, check em out, but you asked about the Ford, and I can tell you that Ford trucks have always been good to me. Good luck, and keep us posted.
Carl
2007 National RV, Sea Breeze