When I started out in business on my own, my experience with websites had been very Microsoft-centric. That is to say, my programming language had been Visual Basic, moving on to C#, against a backdrop of various Windows operating systems. Linux intrigued me, but I didn't know if I would take to it.
The process of finding fast, cost-effective hosting for customers meant that we tried out Linux hosting and PHP, the standard web programming language on Linux at the time, and now perhaps THE standard web programming language.
Linux hosting meant finding out how to mess with all sorts of settings files, examine log files using the command line, etc., grimacing but all the time knowing that there's no graphical user interface (in the case of our web servers) hogging processor time.
The downside of Windows has definitely been memory hogging by Windows applications, and the occasional service pack or security downloads killing innocent bystanders (like the MySQL database) in its wake.
Using Linux, though, means not being able to use c#, a most thorough and elegant language with a very well organised library of supporting functions.
So we do Windows and Linux, and we love it.