The problem with the 6.0 when it first came out, was it was Fords first electronically controlled diesel. The Ford techs really didn't have an idea on how to fix them. They did a lot of trial and error and a fair amount of early models were guinea pigs for the techs. A lot of trucks were ruined by guys that just didn't know how to fix them, although they will blame the tuck. International and Ford tried to quickly train up everyone and right the ship. They did eventually.
With this being the first electronically controlled diesel, the turner world really exploded because now with a tune, one could get 150 extra horsepower with just uploading a tune. There was not a real knowledge base on knowing what injection duration was and how it can blow an engine, they just turned up the fuel and lots of problems happened. Now most turners know how to keep the engine safe, back in 2004 it was the wild wild west.
The other thing I like about the Ford 6.0, every fix can be done with Ford Motorcraft parts. A person doesn't need to know a lot about the after market companies to fix their truck. They are also pretty easy to work on. Most guys can work on them in their garage without a lot of specially tools.