I have not used it, but its advantage is to yield less frontal and lateral swing compared to a classic strap with same movability of the camera to the head.
As disadvantage I expect the strapping of a shirt to the body and thus a reduced ventilation.
I see it as good for photographers on the move, but not as standard strap. What way are you using it?
Too much strap; too constraining. I wouldn’t even consider such a strap. Traditional neck strap works best for me. Hope this works well in your environment and application.
I have often wondered about a chest harness. Frankly wandering about upright in a small area such as a wedding venue is one thing with just a neck strap but a few hours wandering around the outdoors with a P654N swinging back and forth from a neck strap can get very tiresome