I use mine 30/70. I like it at dusk and the mornings. It does take getting used to. Perspective is different.Not very often to be honest. It actually gives me a headache. I turned the brightness all the way down but that did not help either. I think my brain knows there should be rear seats and the rear window in the view of the mirror so without that it makes it all confusing.
I did use it a couple times when the back was loaded and the rear window was blocked. Other than that I do not really use it.