I don't mind the margins, in fact it annoys me a little when there is none (as somebody said, everyone is different), but the main problem with ePub is that one book will have no margin, and the other will have huge margins that eat up half the screen. Same with the fonts, they are all different and different sizes. I often read several books at the same time, and I don't want to have to adjust the Opus' font size each time I open a different book.
I suppose it's the same with paper books (different fonts and layouts), but then paper books are produced by professionals who know to avoid combinations that hinder reading. When ePubs are produced by people who know what they're doing, I will gladly switch.
