I migrated to OS X partly because of the huge hassles involved with using open source software on Windows, but also because of its looks. Apple's cold elegance is definitely preferable to Microsoft's slick, fake smile.
Ubuntu, however, is likely to be my new home. After having Ubuntu and the 3D wonders of Beryl demonstrated to me by Vancouver open source evangelist Scott Nelson, I was blown away. Linux is now not only free and functional, but is fun and looks great.