When considering purchasing a 6.0....
FIRST- Get an OASIS REPORT from Ford (equivalent to GM's VIN report). Do not buy a 6.0 without one. Look for recurring issues and major repairs on the report.
If you don't run a programmer / tunes, and the OASIS doesn't show a history of head gasket issues, then it likely won't have any problems running stock TTY head bolts. I haven't had studs on either of my trucks and neither has had head gasket issues.
Fluids and filters are important to the 6.0, especially the oil. Fresh oil every 5,000 is a must, since the high pressure oil system (used to fire the injectors) shears oil rather quickly. USE NOTHING OTHER THAN MOTORCRAFT/INTERNATIONAL/RACOR FUEL FILTERS AND OIL FILTERS.
The injectors are not nearly as troublesome as the rumors suggest. If you keep the fuel pressure up (as noted below), change fuel filters every 10k, and change the oil every 5k, you will probably not have any more injector issues with a 6.0 than you would have with any other late model diesel.
A coolant filter should be installed immediately to prevent plugging of the oil cooler and the eventual rupture of the EGR cooler.
Fuel pressures need to stay above 45psi (measured in the underhood fuel bowl) to keep the injectors healthy. A healthy stock fuel pump will maintain fuel pressures between 49-53psi under all circumstances.
The Torqueshift trannys on these trucks are as stout as the blessed 4L80E, maybe even more. The trannys they used to have behind the 7.3s are the ones to watch out for.
The variable vein turbos can get sticky if they're not exercised on a regular basis. Not a problem for me, since exercising the turbo is part of the fun of owning a turbo diesel.
The most important parameters on the 6.0 are EGTs, fuel pressure, EOT, and ECT. Keep the fuel pressures over 45 psi at all times. Keep the cruising EGTs under 1250 (short spikes to 1500 won't hurt, but don't make a habit of it) and let them fall below 350 before you shut down. Make sure the oil temps are within 15 degrees of the coolant temps at cruising speeds. If they're not, you need to replace your oil cooler or risk blowing the EGR cooler.
And as far as comparisons to the 7.3 go, the 6.0 will run circles around the 7.3, but the 6.0 will not take abuse nearly as well. When properly taken care of and maintained, the 6.0 will work harder and last just as long as a 7.3.