We have the sun odt plugin installed sitewide.
Sun ODF Plugin for Microsoft Office - Get It
and we already have hundreds of ODT files onsite so it would be really simple to switch. (a reg key sets it as default save format :)
The blatant SIMS lock-in is the only technical reason we keep MSOffice. All teaching depts we spoke to have no problem with using OOO instead.
Eventually MSOffice will wither on the vine as it becomes less relevant. Most people don't know the difference, and the ones that do soon see Ooo has more features that interest them than MSOffice (2003) anyway - I mean the actual useful features like save to pdf, convert to wiki format, use a mysql database rather than having a facelift.