One of the interesting points made in that long Vanity Fair piece about the F-35 [1] is that drone operators just don't have sufficient field of vision to make assessments that a human pilot loitering over a battlefield can. I don't doubt that we'll get there eventually, but I think it's a pretty interesting argument (albeit one advanced by an A-10 pilot.)

[1] http://www.vanityfair.com/politics/2013/09/joint-strike-figh...