I have been driving an '06 2500 Hemi 2wd Quad LB for almost two years (and 80k). Average tanks are 13-14 mpg, to be fair I am not light on the pedal but when I am and cruise at a decent rate of speed on the highway I have squeaked a couple 16-17mpg tanks. Take into account that I always have ~600-800 lbs of tools and equipment in the truck AND it has a fiberglass cap. Plenty of power for the size of the vehicle, tows my Frontier on my car hauler well and tows my 21' boat well. I like the heft of the truck and think it handles well, but then it sits a lot lower and weighs more than the truck you are looking at. '07-later Hemi engines have MDS (multi-displacement system) to save fuel, I have a coworker with an '07 and he does get slightly better mileage than I do.
Mine is an ST with the cheap seats so I can't comment on that too much. The later instrument layout is not at nice as the '03-'05 arrangement for sure. I think the truck overall is cheap. The paint chips like hell all over the place and the windshield has not worn well at all. After a year it had more pitting and damage than my '02 F-150 had in 4 years of driving the same roads. It is also a very loud truck inside. My old F-150 was very quiet as compared to the Dodge, and the stereo was better.
Mind you I am not saying buy Ford, if I had a choice (it is a work truck) I would get a Chevrolet since my dad has had 3 of their pickups and I always like them a lot.