I tow ~6000 lbs quite a bit in the fall. I get wood pellets for myself, a friend, and sometimes my mom - two tons at a time on my 16' Big Tex car hauler (no dovetail so it works okay with a forklift loading pallets). All the kinds I like are from places too far away to deliver.
I'm on my third F-150. The EcoBoost engines are incredible for moderate towing. They make so much power low in the rev band that I can keep it under 2500 RPM even on long steep hills when towing. People say they get worse mileage when towing than a V8 does, but I haven't see a substantial difference when comparing with friends with Silverados or another friend with a 5.0 F-150.
I currently have a F-150 PowerBoost and have only had the tractor and trailer behind it so far (~4000 lbs). I can't wait to try it out with more since this truck has a substantial power bump over my last one - 570 lb ft of torque.
I've had ~10,000 lbs behind my last F-150 and while power wasn't an issue, it just felt like a lot of trailer for the truck and isn't something I'd want to do often. I had similar experiences with a friend and his Silverado 1500 on a long distance ~9500 lb tow. For regular towing under 7500 lbs, though, I think a 1/2 ton is ideal.
In Ford world, you can often get a similarly optioned F-250 for less than an F-150. I considered that at one point, but my truck is also my daily driver and I don't want the burden or fuel economy of a larger vehicle everywhere.