There isn't much of a training cost associated with upgrading to Windows 7. The Start Button has been replaced with a round icon, true, but it's in the same position and the start menu, itself, operates much as the one in Windows XP. Upgrading to Windows 8, yes, is a much more involved process and would involve much more user training.

But, really, that's just sidestepping the issue. The real issue is that user documents are in Microsoft Word, Excel and Powerpoint formats, and, despite improvements, Open/Libre Office support for those documents is not nearly good enough to support moving to Linux full time.

This actually leads to another question I've had. We see all these announcements about cities, states, and regional governments moving to Linux. Of those, how many actually go through with the move? How many have stuck with Linux 2 years out? 5 years out? It's impossible to say whether Linux is actually viable on the (corporate) desktop without knowing if these Linux migrations ever actually take place, and, if they take place, whether Linux manages to stick, or if there's another migration back to Windows once it becomes clear that Linux doesn't yet do the job for end-users.