I have 6 6.0's. My personal truck has 181,000 miles on it. All of mine are 06's, except for one '05. On my truck, I have had to replace a couple of injectors, do the EGR, transmission and the radiator overfow. For what it is worth, I had the tranny rebuilt at about 140k miles, and they said it was the first one they had seen with that few miles on it. Something about spinning the tires towing a wash tire being hard on the tranny. Sounded like a weak excuse to me.
As for the others, so far, I have had really good luck with them. I have not had head studs put on any of them, or head gaskets. They have been absolutely reliable. I know that others have had problems, but that has not been my experience. I do think that the 6.0's are engines that like to work, and be run hard. Sometimes I wonder if guys are being so careful with them, that the first time they get after it, they have problems. Just my opinion. I know my guys want the older trucks before they get in the 2011's because of the engine. I don't know why, because the 2011's are very nice, they just have gas motors.