Well, I've owned an 11', a 15', and a 21' 3.5 ecoboost and we have many in our work fleet so I'm pretty experienced with them. I pretty much always have the cruise set at +5 mph over the speed limit and I typically rack up 35k-40k miles per year.
Mileage wise, with the 3.5 you can expect 17-22 mph unloaded. I've done much worse driving faster into really ugly head winds and I've seen over 27mpg with a big tail wind and a light foot but the range I posted is what I see on a regular basis. I would expect the 2.7 to do a touch better, we have a few of them in the fleet but I don't personally drive them enough to give good first hand experience. One thing I've always noticed is the big mph swings you can get with the ecoboost. As soon as you start building boost, the mpg drops quickly. So although they can have a really high mph cap, it is effected more by wind, load, and other conditions than say a regular V8. Hook a trailer up and your going to be in the boost unless it's something really light with little wind resistance like a 16' aluminum boat. I did recently put some E rated 34"x11.8" BFGs on my 21' and really noticed I took a mpg hit with those, much more than I expected. They seem to have cost me a solid 2-3 mpg! food for thought.
Power wise, there's no shortage, they are just plainly phenomenal. There isn't another gas powered 1/2 ton that tows like an ecoboost, not a 5.7hemi and not a 6.2 GM. The low end torque is irreplaceable if you tow much at all. It's the big reason I keep buying the 3.5. I think the 2.7s are way underrated on power though, they seem almost as peppy as my 3.5s with a bit less torque, at least thats the feeling I get driving them empty. Reliability has been great. The number one biggest thing that we noticed is they are very hard on spark plugs. Plan to change them around 75k miles. Not sure if it's the direct injection, higher cylinder pressures or what, but just about all of ours have had run ability issues where they are missing long before 100k miles and I think every single time a plug change has fixed the issue. Use good oil and change often, keep a clean air filter, and they'll run as long or longer than any other pickup engine. Most of our fleet trucks are very high mileage (150k-225k) and none have had any major engine issues. Plenty of other stuff, like all vehicles, but the Ecoboost itself has been a solid runner for us.
Obviously my experience is with the 3.5 for the most part which was out many years before the 2.7 however the 2.7s that we do have, have been good so far. Good luck.
