I guess the only point that will not change, among the points above is the angle/nature of light, and its effect on screen. When you get it right, it is amazing, but there is a noticeable difference between other conditions and this "perfect" condition, which is kind of irritating for me. Also I sometimes get the feeling that a page does not look as good as the previous or next one, especially if the general ratio of black/while in the page changes.
Maybe I'm getting too picky
Kind regards
Seref