Reading is more comfortable when the text is not sized to the entire screen (cite below, with more references). Also, witness the number of window managers that offer ways to facilitate half-window views (i.e., XMonad, Cinch or SizeUp, Windows 7 window snapping, even Ctrl-X 3 in Emacs, so on and so forth).

http://psychology.wichita.edu/surl/usabilitynews/72/LineLeng...