From E-Commerce News (in an article on OpenOffice):
One of the most compelling reasons to use OpenOffice, according to the project’s supporters, is that it can serve as a testing ground for an eventual switch from Windows to Linux on the desktop.
Once users have migrated to OpenOffice, the reasoning goes, switching to Ximian Evolution, a free e-mail and group calendaring application, and Mozilla, an open source Web browser, becomes easier. And once those transitions are complete, removing Windows entirely and replacing it with Linux becomes less of an issue.
This is a very good idea: make it step-by-step rather than one dramatic change.