I can usually get away with four. I use one for internet, a second for
management tasks, a third for multimedia and the fourth for office. I don't
bother to name them. I just keep them separate in my head. I like four because I
use the Compiz cube. If I used more then I would have to go to the cylinder. :)

Windows users are not used to virtual desktops, but they are really handy. I
rarely have to minimize anything. I can do several things at once and can switch
between tasks with a key press or the mouse wheel. When I have to use Windows I
find it frustrating not to have virtual desktops. If I used it regularly (I
don't), I would install a Windows virtual desktop programme. Microsoft makes
one, but they have not added it as part of Windows. They once said that tabbed
browsing was not useful either, but now they include it in IE. Maybe they don't
want to look too much like Linux.