In 2005 I made the switch from Windows XP to Mac OS X. My experiences with it were refreshing. The interface was well designed and ease of use was great compared to what I was used to with Windows XP. At the time I was looking for anything more enjoyable or easier to use than Windows.
During my switch from Windows to Linux I tried many distros and desktop environments along the way. As far as desktop environments I like KDE and Gnome3 the best. Sure they are probably polar opposites of each other, but both stood out to me as different enough to get me to like them.