Richard Cazenave (Congressman, UMP, right wing), is the French congressman who has managed to prepare the switch from Windows to Linux of the French Congress (Assemblée Nationale). He is interviewed by TicNews :

I personally use, Firefox, Thunderbird, Sunbird and VLC on my laptop, running Windows ME (it's a bit too old to migrate it to Linux). But my wife's computer – like the ones of my team – run Xubuntu! Experience has taught me that it's easy to switch to a new Operating System when the applications that you are used to use daily are the same or very close to the ones you'll have on the new platform. I think that, Firefox and Thunderbird, because they are easy to use and available under Windows, Mac OS and Linux, can help people move to another Operating System.

And another quote, while Mr Cazenave answers why he wanted the Assemblée Nationale to use Linux:

I wanted this mostly to solve the issues of standards, as I think that public organizations and administrations, in order to be able to be used by everybody, must use tools that implement open standards. It's a matter of compatibility over time as it ensures that any software vendor is going to be able to implement this standard. It's also for financial reasons, as the use of Free/Open Source software, considering the size of these organizations and administrations, enables significant savings, despite the cost of deployment, migration and training involved. I hope that Assemblée Nationale will lead the way for others.