1. The typeface Garamond - I like it because it is gently old fashioned-looking, but very spacey, so its pages are light and airy.
2. Automatic page numbering. Anyone who has ever worked on a system that for some reason or other doesn't do page numbers by itself will know what a pain it is -- one little change means forty little changes.
3. Magnetic ruler guides. In publishing software, they help you to line up text boxes by catching hold of them when you move them about. They are usually green, and my screen is always criss-crossed with them because on paper text at different heights drives me mad, but on screen I just don't spot it.