I have a 2003 Excursion with the 6.0, it has just over 230k and AFAIK it has never had headgaskets. I bought it with around 190k on it, has been a great vehicle. Granted I HAVE spent some $$ on it, but I agree with others here, I'd rather buy a $9k vehicle that was in VERY nice shape and ran great, spend some $$ on it, and have one that is 'upgraded' as I spend $$ to replace parts. My brother-in-law recently bought a 2000 Excursion with the 7.3 for about $14k. I can promise the 6.0 will run circles around it.
Stuff I have done:
Upgraded to 05'-07' suspension/axles
front mount oil cooler
remote oil filter
EGR delete
4-gauge pod with Isspro gauges (EGT, boost, fuel pressure, trans temp)
4" turbo-back exhaust with muffler (I hate straight piped ones)
new 155cc injectors
SCT tuner
and some cosmetic stuff (front bumper, grille, etc)
Including all the above I have less than $13k in it (I really don't know what I have in it)
It DOES currently need headgaskets/studs. That will put me out about $3k. I installed everything else myself but I will have the headgaskets/studs done by a local guy.
I have no regrets buying a 6.0, BUT you have got to plan on spending some $$ on it, but NO vehicle is bulletproof, they all have issues.