I'll pipe in here, mainly because I can and because I haven't seen much on the NEW fords, only the 7.3's.
We're coming from an 09 Silverado 2500 with the 383 and the Allison tranny. while it was a good truck and was pretty well loaded for a complete and total base model, it wasn't really up to the task of towing a 9K+ pound 26 foot enclosed trailer. While headed to Lincoln from Wisconsin, my pops averaged 7 MPG at about 75-80 mph. I averaged 26 in the Z06....
Anywho, he stated that it was screaming up hills (4000 - 5000 rpm for a few minutes going up hill, losing speed) and ended up taking a longer way home fore the sole reason that it was more level ground.
Recently, we stepped up to a 2010 Ford F250 with the twin turbo deisel, and so far it's been pretty good. I've towed the car trailer with the old truck, but we have yet to hook it up with this behemoth. It's the Lariat edition, so it's significantly nicer than the base model Chevy, but it still has a few quirks that make me wonder what Ford is thinking (stereo that is beyond basic, hasn't changed much since my 2000 F150, solid front axel, and a few other odd items). Overall though, the interior is pretty well put together and the truck is an absolute tank.
I hooked a 6000 lb loaded trailer up to it (open with a tractor on it) and it towed it like nothing was behind it. The Ford has the best power numbers at 650 ft. pounds of torque, which was definitely noticed when I hammered the gas. it's also got a 5 speed torqueshift transmission, which appears to be strong and shifts well. No complaints with the engine or transmission, but the truck also has a grand total of 1600 miles on it...
As far as the gas mileage.... Once the EPA came out with the new emissions standards for diesels, the trucks have gotten hammered for mileage. I saw a high of 18mpg, towing the empty trailer up to Door County I got 16, towing back I got 12-13 (200 miles each way). The fords have this goofy ass exhaust filter that periodically needs "cleaning" if you let it idle too long. Ford accomplishes this by dumping raw fuel into the exhaust to burn the filter clean. This seems to happen semi-frequently and really kills the milage. Periodically it happens while driving too, and then you can watch the mileage drop to about 9. I fear that the days of the super fuel efficient diesel are gone, or at least it'll take a while before they come back.
One more thing... When driving, it's important to keep the truck out of boost. I've noticed that when the boost gauge goes about 10 psi (I've seen 38 psi max) the milage goes down pretty quickly.
I have an 08 F250 FX4 twin turbo with 33,000 miles on it and I have had zero zilch nada problems with it. I was a previous owner of an 04 powerstroke Ford that was at the dealership at least twice a year with turbo or EGR problems so I was reluctant to buy another Ford. I held my nose crossed my fingers and bought any way and am glad I did it. The 6.0 really hurt Ford with it's reliability problems and I think they really worked hard to make the 6.4's better.
The interior on the 08 is as good or better than my BMW and the power is great. I pulled a 11,000 lb enclosed trailer over the rockies on I70 with it with no problem flattening that hill even at 11,000 feet. My buddy was commenting that his Chevy pulling the same trailer the year before couldn't touch the Ford for pulling power.I went with the upgraded stereo and I have to say that it's the best sounding factory stereo I have ever heard. It has the touch screen and built in Sirius and blue tooth. Really sweet.
The only down side is the Exhaust filter that seems to have taken about 1 mpg away compared to the previous truck but I bought the truck to pull the trailer comfortably down the road so I'm ok with that. Rumor is the new 6.7 with reverse flow intake exhaust system keeps the DPF (Diesel Particulate Filter) hotter and boost the mileage back to the non DPF equiped trucks range and with 400 hp and 700 tq.to boot. Well see if the mileage rumors are true or not.