Munich is struggling with their Linux migration from Windows. The article talks about the difficulties that they are having. I understand that moving all of your systems and users to a new platform is difficult. It is always a lot of work and planning to migrate users on the same platform let alone on a new platform. There are many hidden costs like training and application compatibility. So moving to Linux may not be the big cost savings that people envision. Munich is a good example.
Microsoft's Get the Facts site.