My 07 has been a nightmare so far at 37,500 miles. Love the truck though and hope things get better. Head gaskets, oil leaks, wire chaffing. Left me stranded twice. Bone stock and all maintainence. Ford did step up and give me the 21 point, 200,000 mile warranty for my trouble. My main gripe is that every time I had a problem, it took at least 2 trips to service to fix it and my oil leak has not been fixed yet, just going to live with it for now. I would try to get some sort of extended Ford backed warranty on any used 6.0 as they cost a fortune to fix if on your dime.
Bill