I had 20 plus rental cars last year and very few had tech features I would ever pay for.
Lane assist with adaptive cruise are the only notable features for long drives. I did enjoy the red dash notification Toyota has. Totally caught me off guard the first time however, I tried out the ABS.
The other thing I'd like to see more or less mandated is blind spot warning. I especially like the kind that is visible to other drivers. I don't even have it on any of my cars, LOL. I just like to see it on other cars that I'm passing.
Lane assist I am ambivalent about. I had AP, it was okay. It does not drive as defensively as I do, however, which meant that it increased my tension on long drives rather than reduce it. I do like good adaptive cruise however. That means no phantom braking :).
It takes some getting used to, but once you learn to back via mirrors you won't want to twist around anymore. You do need to check behind the car beforehand because you cannot see directly behind you and thus might hit something on the ground. However you get much better visibility to things that are moving from the side to behind you, and that in my experience is where the danger is most of the time.
I do favor backup cameras though. They show you things you would miss either twisting to look backwards, or looking in the mirror.