Old guy take on this - We have had several cars with 3-D cameras and frankly, I am not sure they are terrible useful. However, the front camera and grid on my 5BW is great and helps me park in our rather tight garage. I use the front and back cameras a lot, just not sure I trust / use the 3D view much.
I was looking forward to the mirror camera as I thought that would be a great addition. It got turned off within a few miles of leaving the dealership. Explanation - I wear variable focus lenses in my glasses and when I glanced up at the rear view mirror, I got brain freeze. The mirror is rather close and when I glance at it, I am using the distance part (top) of my glasses and the mirror video is just a fuzzy mess. I have to move my head up and down to find the section of my glasses that brings it into focus. With a mirror, the focus distance is the sum of the distance from you to the mirror plus the distance from the mirror to the object. (ok, I had to look that up but curiosity got the best of me). Therefor the mirror appears in focus while the camera view doesn't using the distance part of my glasses.
I know most of you could care less about this and I wish I was one of you but for the old guys, just a bit of useless information.