Well... old dog, new tricks.
After reading this thread, a while ago after it first started, I set my 5Dii and 7D up for back button focus. It took just a little bit of getting used to, but... overall, I'm very happy with keeping focus and AE/Shutter on different buttons. Best thing, is you get to focus, then compose and shoot multiple shots without having to worry about the camera re-focusing for every shot. Simple. I can always touch up the focus with the touch of a button. This is how we tended to shoot in the film/non-AF days. You'd focus, then worry about exposure and composition. Like I said, old dog, new trick. Every once in a while still... I get caught off guard, but it only takes a very brief moment and I'm on my game again, and thumb is on button to focus. I can't see going back to having it all on the shutter release.