Yes, you can look across your shoulder, but you can hardly twist your neck 180 degrees. And if you can, you certainly cannot look ahead at the same time, shifting your glance quickly between what is going on behind the front screen and in the mirror. You asked for opinions, and most of us have disagreed that it is a good idea to scrap one of the sources of information. But of course, every man to his own, and surely it is not illegal. I just do not see any significant benefit, only disadvatages.
