Tried out EC with those cameras and, yes, it worked… Just not for me. I found I tend to look all around the viewfinder, not just at the subject I’m focusing upon. I am checking composition and looking at what else is in the frame, not just staring at the subject constantly. That’s essentially what you have to do for EC to work best. EC was tracking following my eye and continuously refocusing at different distances. I found it to be a pain in the butt and more of a distraction than a useful tool, so after about 3 months trying to on my EOS-3s, I turned it off and never used it again. My “keeper” rate of in-focus images immediately improved. After I learned to use Back Button Focusing, my keeper rate went even higher and that’s how I’ve been shooting with Canon cameras, film and digital, for over ten years now.

So I think of EC as a gimmick… Some people will find it fun to use and useful to an extent. I don’t think it encourages particularly good habits or makes for more in-focus shots or faster shooting.