I don't have a Biodiesel truck, but I do have a VW Golf Diesel that runs on Waste Vegetable Oil.
I have over 80,000 miles on vegge oil, and I love it. Last year, I went on a trip from MN to Arkansas, and by the time I got back home, I used 4 gallons of diesel. The rest was all vegge oil. 3200 miles before I had to refill the diesel tank.
My Golf has 2 tanks in it, one for diesel, one for vegge oil.
If I could find a reasonable enough diesel truck, I wouldn't hesitate putting a vegge oil conversion kit into it. It would be a heck of a lot cheaper for me to take my boat out fishing.
Cheers!
Wade