I find the latency of these things to be really bad, and the "wide-angle" view is never wide enough (and what is with all of the parking guide lines they draw that never seem correct?)

...but then most modern cars seem to have abysmal visibility through the back windows anyway. The rear view from a 20 year old Micra I often drive is excellent, much better than any of the more modern cars I have hired.

I've never had one and I've never backed into anything without it.

I'm not really opposed to reversing cameras by themselves, but a) it takes up dashboard real estate for a feature I don't really use, and b) as soon as you put a screen on the dashboard, the company is going to want to put all sorts of annoying "features" into it.

As an additional feature, yes, not as a replacement. The great thing about actual mirrors is that they don't need power to function and they can be replaced with any other in worst case.