You brought up your mom and Linux, not me. Sure, medium to large companies have IT support and HelpDesk, but guess what, it costs more to run desktop support for Linux because a) you have to get rid of all your MS support people and hire linux qualified people and b) Linux admins/techs by and large don't have a history of creating a culture tailored to supporting other people. That means procedures, standards, and corporate distributions must be created where none existed for Linux desktop before.
Open Source exists for developers to scratch an itch or to boost their rep. The attitudes of many power Linux users is that anyone who doesn't know how to do something should RTFM or they are an idiot. Ease of use? LOSER! You should just look at the help newsgroups or IRC channels sometimes.
I don't see why you want to bring OpenOffice on Windows into this. The original article is about replacing 14,000 Windows installations with Linux. The cost savings ain't gonna materialize, and trying to setup techsupport for 14k Linux boxes and associated problems isn't going to be easy.
Many large companies don't even upgrade from NT4 to 2000 to 2000 to XP, or even Service Packs, because it generates (invariably) a huge number of trouble tickets and causes more trouble than it is worth alot of times (modulo hotfixes) The belief that Linux will solve this issue is pure naivete'
The cost of Windows is an insignificant fraction of the support cost of a corporate user.