Gnome, and in fact, all Desktop environments in Linux.. in all distro's uses up far too much screen real estate for just about everything.
I don't know enough about Linux to really identify the problem. I do know that an 8px font in Windows is hard to read, but an 8pt font in Linux is perfect, if not a little large for alot of things (icon text in nautilus, window manager text, panel bar text, etc..)
Icons are too large. Default pidgin conversation windows are too large. The panels are too thick. The toolbar buttons in Nautilus are far too big.
Compare a 1600x1200 screen in Windows, to one in Mac to one in Gnome or KDE. There's far more space to work in other OSes.
I don't know if it's desktop design, poor video drivers, bad font rendering.
I know that if I spend about 30-45 min tweaking with firefox themes, gnome settings, and individual application settins.. i still cannot get the same screen space to work on that i can with other OSes.
Also see:
http://ubuntuforums.org/archive/index.php/t-338007.html