First of all, I don't run Win/Apache it in a production environment. I don't run a fulltime server at all (I'll let my hosting company do that), and if I would, it would be running something like FreeBSD or Linux. At work we all work on Win2K, our fileserver is Win2K, but webserver and databaseservers (which are vital offcourse) are all running SuSe Linux.
Second, Apache is quite stable, even on Windows, and it kicks IIS' ass big time, so why wouldn't I use it? I won't install Linux just to get a testserver running, and I sure as hell won't run Linux as a desktop system...