Really...I think that a guy has to spend a few thousand bucks on a 6.0 and they'd be mostly good to go.
I quoted an EGR cooler and an oil cooler replacement on a 6.0 the other day and if I recall, it was $3600.00+tax. If you mod it to make more power...you should plan on blowing head gaskets...at which point, do an ARP head stud kit instead of the stock head bolts. Not sure I'd recommend worrying about the head studs until/unless it blows the head gaskets.
If you don't mind working on it, have the tools and the skills to fix what breaks, go for it. They have a world of power and get decent mpg's.
I guess I'd also plan to put lower or all the ball joints in it at some point too.