I was a Windows "fanboy" for a very long time. Whenever I would use a Mac I was disgusted and annoyed, but some recent changes have happened. I got a "job" that required me to use Linux, specifically Ubuntu Linux. I did mess with Ubuntu a little before, but I was never able to make it my primary OS because of the lack on Windows programs. When I was required to use Ubuntu a lot for my "job" then I used Wine to run a few Windows apps, but I mostly learned how to use the native apps. Eventually I mainly used webapps and an IM client native to the OS. At that time I didn't really have any dependence on platform-specific software. I was able to learn the internals of Linux much better so I felt a lot more "at home".
A while after I was OS independent I wanted to do some video editing. I did have some experience with Final Cut Express so I didn't want to learn a Windows video editor on a project that I already had very little time to do. I obtained OS X and Final Cut Express and found it easy to go a few days without using Windows or Linux, but I did hate almost every minute of it. On Windows and Linux the keyboard shortcuts make sense, but on OS X they are much slower to use than on other OSes. It's not because I wasn't used to them, it's because they are illogical. To take a screenshot you don't push Print Screen; it's like Command+Shift+3. That's just one example, but there are many others just as painful.
But after all this experience I have found that when I do not have a specific goal I use Ubuntu Linux. Ubuntu is a bit faster than Windows. Compiz Fusion is the main reason I like Ubuntu; I have no complaint of pretty graphics (and even a lot of useful features). Also I really like that it's a free OS; I don't need to pay $200 or $30 every few years. My only complaint is a lot of software works like it's free with quite a few bugs.