My 09 2500 QCLB 5.7 3.73 with stock 265 tires regularly turned in 17 mpg figures highway. After leveling, Ranch Hands, and 35's (& speedo cal) it dropped to a consistent 13, although would hit 15 occasionally (presumably with a tailwind).
Put over 300k on it. It ate the cam and lifters, wore out the limited slip in the rear end in the 180-250k range. Was showing signs of repeating the engine and rear end failures when the trans started slipping. I was planning to fix it again but when the AC took a dump I dumped the truck.
It was comfortable, rear seat legroom was lacking in the QC. I enjoyed the power of the Hemi, it was adequate for the truck. It would have been happier with 4.56's. All that said I don't regret my time with it but I don't regret getting rid of it either!
I like my V10 Excursion much better. Not as peppy as the Dodge was but more comfortable and practical even if it's not quite as fuel efficient.