@number6 >Not that I would defend M$
Unfortunately, you just proceeded to.

>the cost of the operating system and the software is a fraction of the cost of the machines it runs and and the personnel that use it.
You might think that, but m$ very carefully ensures that everything from then requires payments of a fortune, so the software rent alone is a large portion of the huge TCO (Total Cost of "Ownership"), although the cost in the amount of time wasted in trying to get work done with m$'s slow and broken software is huge as well.

>Retraining thousands of employees to use Open source products might be more expensive than the cost of the operating system & software.
You say that, but one army tested how well people could use microsoft office (whatever the writer application is called) and libreoffice writer and found out that usability was the same.

The basic functioning of the programs is the same - the menus are somewhat different on libreoffice (thanks to patents, but the layout is actually better as I noticed) and really, the only retraining required is to let the wagies know that a new word processor will be used from now on and to tell them to get working and they're getting paid to work out the new menus, including searching how to do things in a search engine if required.

The cost of escaping from lock-in may seem high at the start, but once you actually itemize the costs, you will realize that the vast majority of switching costs are created by proprietary sabotage and a fortune will be saved over the long term (within 3 months actually).

>Then there's the problem that almost always there will be essential software that only runs on MS desktops.
Yes, there will always be lock-in of some sort, but I don't believe any truly essential software that only runs on windows remains (WINE support only improves, but really I can't think of anything you would want to run in that aside from notepad++ maybe).

>And then there's hardware compatibility issues.
GNU/Linux actually has far better hardware compatibility than windows, unfortunately there is indeed some hardware sabotaged by the manufacturer so it doesn't work with existing drivers, but support for even such broken hardware only improves over time.