Grassman, keep the 7.3L you can get more MPG out of that old engine then out of the new 6.4L.
Yes the 6.4L has had some issues at the beginning. But that is with any new engine or redesigned vehicle.
I think the 09 6.4L is better then the 08 6.4L but what do you expect after a year of being on the road.
Yes ford did do a big road test and had there own drivers driving the truck and pulling a trailer all over the country. But again that was done by Ford with Ford Employees driving it. Not by the common person who is going to beat the living crap out of there truck.
For me I will keep my old 2002 7.3L until I can't afford to keep it running any longer. I got 161,000 miles on it and it still is pulling around 21 mpg on the hi way and around 16-18 mpg everyday driving.