Why is Linux (and FOSS) better than Windows?

Obviously, this could start (and has started) plenty of religious flame wars over the years. This is not my intention. I am wondering what points I can use, specifically, as arguments to make a case for FOSS, specifically Linux, in a business setting. If I were hired as the IT director of a small company, and was asked to build an IT infrastructure, my inclination would be to begin building with Linux and FOSS, but when my boss came to me and asked me why I chose those technologies, honestly I would have very few concrete reasons.  Here is what I have so far:

  1. I agree with the philosophy behind FOSS
  2. There are a plethora of plugins developed to help extend our infrastructure for our current (and future) needs
  3. If we find that a piece of software we downloaded (or purchased) is broken, or doesn't do what we need it to do, we have the source code and (hopefully) the resources to fix/change it.
  4. Not only are there several (competing) options for paid support, there are a ton of free message boards, mailing lists and IRC chanels to get assistance from, making our virtual knowledge bank HUGE
  5. Total cost of ownership is going to be a fraction of that of closed source products.
  6. When needed, we can find closed source software to do what we need when we can't find a FOSS solution.

That's where I am at. I am a programmer and know only the basics of networking, so the networking possibilities within FOSS elude me. If there is anyone with suggestions, please leave a comment.