Typical users usually don't have much problem moving to a Linux desktop, particularly a KDE-based one that looks a lot like a Windows desktop. The typical productivity apps (e.g., OpenOffice) are very simple to move to as well.
The major problems arise with so-called power users, especially those with complex Excel macros. I recommend that you start with a pilot set of users, perhaps 10 or 15, that reflect all types of users within the organizations. See how they do with migrating to a Linux desktop and base your practices on that.
This was first published in November 2006