Netcraft has produced their monthly rating of reliability of hosting companies. Out of 41 listed, only 5 run that other OS while 24 run GNU/Linux. That shows what happens when people actually have a choice in supplier of software. The best tool for the job gets chosen. Further, IDC reports that M$ makes way more revenue than anyone else for server software so the folks getting the third-best software on servers are actually paying a premium for it… Sad.