If still in warranty stick with what Ford recommends. As for me I go with Chevron Supreme 10W-30. It is what I use in my 98' F150 5.4L and in my 2003 Camry with a 2.4L 4 cylinder. For that matter Havoline is just as good in the same weight.
my 03 5.4 seems to like Schaeffer's 5w30, but it has only been in for about 2,000 miles. I will change it at 3,500 for the first interval and have an analysis done. I will post my results to let you know how it held up.