What sold me on diesel is when my dad's 2003 Ram 2500 Cummins was getting better fuel mileage while towing a 35ft travel trailer (about 12mpg) than my 2004 Ram 1500 with the small V8 during normal driving(about 10-11mpg). The best I ever got out of that truck was 14mpg when I filled it and jumped right on the highway for a 200 mile drive.
So now I have a '13 Ram 2500 Cummins and love it. I get close to 20mpg as a daily driver, have seen as high as 22.5mph straight highway driving, and 11-12mpg towing that same 35ft travel trailer. Yeah, oil changes can be expensive, but they are only required every 15,000 miles. And fuel filters need changed about once a year, but that's fairly easy. So I don't see maintenance as a big deal.
That being said, the new gassers are a lot better than they were 14 years ago when I had mine. And that 6.4 Hemi is supposed to be a beast. I'd like to hear how they are on fuel mileage as a daily driver.