Just read an article about the experience the City of Munich is having in migrating from Windows to Linux. Apparently, the migration project has run into some serious snags and cost overruns in the areas of secuity, compatibility, and stability. They're also getting hit harder than they expected for training costs.
The city council is demanding an investigation, since they were promised “cheaper”. Apparently some people have forgotten that even during the final project bid process the Windows solution was known to be less costly, since Microsoft apparently dropped trou' on pricing.
My guess (based on personal experience with Unix, Linux, Windows, and watching dozens of customers try to migrate in both directions) is that, when the project is completed, the City of Munich will discover that the project cost more money with Linux than it would have with Windows even at the original bid before discounting. The cost of becoming ones own operating system development and application testing shop is huge and on-going, to the extent that there isn't enough calendar time to amortize and recover the expense.
(And I so enjoyed reading the comments attached to the article, too. Everything from Linux fanboy flamage to “Microsoft is still evil” flamage to “The playing field still isn't level” whining to... )