Jeez you guys are being harsh
I have been in the game since 1980 at IBM and have keenly watched all major desktop operating systems grow up. They are all different, they all have a different user base and they are all better at one thing or another over some other system.
I employ the best artists I can for our advertising content generation - and the Mac applications beat the equivalent Windows apps hands down. No question that Mac graphics apps are just so much more refined - and unless you were a trained graphics professional - you wouldn't properly understand. (By the way - MacOSX has made use of 3-button mice since inception. The single button mouse has no place at my office - I've always hated them)
I use XP on my office machines.... but I use OpenOffice and not MS Office. Windows does give us some semblance of office compatability with our clients and accountants.
I use Linux and Sun Solaris for our server base. Anything to do with communications and networking just runs more stably and securely under Unix/Linux - I won't trust Windows to run anything in our network-related roles.
So there you are. If you try to hold one of these systems up over the others - across the board - I don't think that you are doing yourself a favour.