Just for reference, my MPG numbers probably suck pretty bad due to a lead foot. On the highway I'm usually at 70-75MPH, and I'm not timid starting off, either.
I believe the 6L diesel would probably get 11.5-12.5MPG if you kept it to 65MPH or less on trips. I also believe it will get a *lot* better with the addition of a $300 chip upgrade. We'll see.
You definitely don't save money on the fuel consumption over the purchase price. But like Karl said, I like the way it drives. I also tow a lot more than the average person out there since not only do I do a lot of national events but I also have a boat and do pinball buying trips around the country occasionally.
Outside what I like, I'm also just skeptical of how well the gas stuff will hold up to 20k miles per year of towing. But it just depends on how much you'll be doing *and* how you drive and how you maintain it and what your acceptable level of risk is. I have no doubts that there are non-diesel options that will be cost effective. I also have no doubt that you'll like towing with a diesel better should you decide you want one.
--Donnie