I have run Biodiesel in the 6.0 and i can say with confidence that it loves it.

In San Diego i can buy B20 from a fuel station for the same price as petroleum pump diesel.
Yes, SB is right in that refined B100 from the pump costs over $3 but i have run it and also "homebrew" B100 and also B100 from purchased from a co-op group(homebrew and co-op biodiesel alot cheaper ,ie, no highway taxes involved)-sold as ,cough,cough....fuel additive.

No doubt about it, the truck runs noticably smoother on the Bio (documented and proven higher lubricity than petroleum based #2).
All that with a nice mild french fry smell instead of the eye burning diesel fumes.

Anyway, the quality control issues SB points are are accurate and yes Ford says B5 only.

Some people think your crazy for putting anything besides #2 diesel in your truck but thats the illusion big-oil wants you to believe.
I'm no hippy and i'm stating first hand that biodiesel is the real deal.
Runs better, perhaps slightly better MPG's and no $$$ for stinking middle eastern oil suppliers!

I suggest you go to biodiesel.org, locate a supplier in your state and try a blend of roughly B20 and go from there.