In 2013 I bought a new F150 XLT with a 3.5 EB and an 8 foot bed. I had been looking and thinking about an FWC for years before pulling the trigger in 2015 (the year I retired) for a mostly loaded Grandby. Despite my research, the five months between the FWC order and delivery was somewhat of a roller coaster in that I had moments of concerns as to how the F150 would handle the job of hauling the Grandby.
It's been about 16 months and over15000 miles later and I can honestly say I'm really happy with both the truck and camper. I live just north of San Francisco and so far my Golden Retriever and I taken two trips to Montana and Idaho, twice to southern Utah and Northern Arizona, Death Valley, Yosemite, down the coast of California, ghost towns in Nevada and several trips steelhead fishing in Northern California. Occasionally the wife goes too, but she's still working so I can live on the road in opulent FWC style
During these trips I have had zero problems with the systems of the truck and the handling, power and braking have all been tested "in the field" and all performed exceptionally well.
As for gas mileage, my average in all the above trips was 13.9 mpg and I'm fine with it. I was just too concerned with gas mileage until I read a post by Park who basically said "Gas mileage be darned. I just fill it up and go" and I adopted that philosophy which increased my level of happiness because there's not much I can do about it at this point. Just heading down the road with the dog next to me and heading to the next adventure is a great thing.
Finally I should mention that I have E rated tires and Firestone Airbags both of which I feel are essential. I don't tow or haul stuff on the top and I try my best to stay as light as possible.
I hope this helps.
Ron