+1Who in the world, ESPECIALLY pros, want to pull the camera away from their face so they can fiddle with a clunky touch screen?
Well, how about pros (or amateurs) who shoot with the 600 EX RT? Or Pros or amateurs who want to change tracking sensitivity or accelerate/decelerate tracking? There are dozens of functions that cannot be adjusted with a camera glued to your face that would be much easier and quicker to accomplish with the swipe of a finger rather than having to work through buttons and joysticks.
People need to open their minds a bit and quit being such Luddites about technology (especially ironic on a forum filled with gearheads). No one has ever suggested that a touch screen would replace the buttons and joysticks, but it is proven technology that would add significant functionality and convenience to enthusiast and pro-level cameras.