That has to be Di2's most amazing feature- a sensor on the front derailleur that senses chain rub and instantly engages the servo motor to tweak the front derailleur so that is stops rubbing immediately. It works seamlessly in the background. That Di2 system is amazing. Works flawlessly, reliably, doesn't break, etc. Shimano got that system right. They sure tested it enough in the pros. Credit where it's due.
Sure it's overpriced. So is my Lexus. What's your point?