I used to be annoyed by people scrolling through their prayers. But now I also found phone siddur useful for outside minyanim… looking for shabbos edition, though.
My favorite mahzorim are two pre-WW1 from different sides of the family, one Vilna, one Wien … good feeling that you follow your predecessors in davening. Wien one is much thinner – less piyutim and much better, thinner, paper.