Not entirely true. While it may run some of the fastest computers in the world, MS still has something like an 85-90% share in the server world.
Try 2-to-1 split in Linux's favor for servers:
Usage Statistics and Market Share of Operating Systems for Websites
True enough, but the average computer user who is semi-literate can administer a Windows server on a day to day basis. The hardcore problems will always require a professional regardless of what the platform is. I've never used a Linux server, but from my desktop experience with it, I'm going to guess that it probably is not as easy to do as Windows Server is.
The average person should not be administering any server, let alone a Windows server.
And, for you: Admin work on a Linux box would be difficult, since you have no experience with it. It would be like asking a person from AR to administer your Windows boxes.
However, admin work on a linux box IS easier. So much in fact, it requires 1/10th the number of admins to take care of a linux farm vs. a windows farm.