I'm a linux user. I've had Linux on my home PC for 4-5 years. I run Slackware and love the hack-ability and hobby-est feel of using this OS. For 3-4 years now, the 'year of the desktop Linux' conversation has been happening with the David and Goliath battle for desktop being waged against Windows.
It hit me recently that Linux is not fighting MS for the desktop. They're fighting OSX. Well, everyone thinks the fight is against Windows, but I think Apple has quietly beat Linux on the desktop.
Seriously - if you were considering a non-Windows desktop for your organization and needed it easy to support, wouldn't you go to OSX over Linux? There's a real company to hit for support, real commercial apps and best of all - all the open source apps will compile against it.
Why would you consider anything else? (Oh, I've never used a MAC)