No first hand experience with Nitto's, but I have a good friend that had them on his 2005 Ram 3500 and got TERRIBLE mileage out of them. If I remember right, they lasted less than 25,000 miles. This friend is terribly hard on everything he owns, but his experience was enough to make me think twice.
I had Hankook's on my 03 before I sold it. I put around 2000 miles on them, and if I was going to keep the truck, I would have gotten rid of the tires. They wandered terribly, especially under load.
My truck has about 37,000 miles on the OEM tires. Will be replacing the fronts next spring, and will likely go to Michellin. I have had the best luck with them in the past.