Quote Originally Posted by Dr Croubie View Post
now that they're including the old optical trigger in every new body (that has an inbuilt-flash at least), there's no need for the ST-E2 anymore, so they needed to come up with a new gadget that we have to buy instead. Radio-trigger it is.
Well...on every body with a popup flash, that is. No optical trigger on the 5DIII or 1D X - nor a built-in RF trigger, either, which would have certainly been possible.

Regardless, Amazon has the 600EX-RT in stock now, and I've just ordered mine. I'll see how nicely it plays with the PocketWizard FlexTT5, although my main use for the 600EX, at least initially, will probably be on-camera or via OC-E3 on a flash bracket.