On TechRepublic there is an interesting article about the migration of Desktops from MS Windows to Linux.
http://www.techrepublic.com/article/how-munich-rejected-steve-ballmer-and-kicked-microsoft-out-of-the-city/?tag=nl.e098&s_cid=e098&ttag=e098&ftag=TRE126e25f
Especially the facts about the real costs are very interesting.