Macros
People just doing word processing and tracking a few numbers in a spread sheet won't have a problem switching to something like open office.
However I don't see the people who have invested time and money into integrated workbooks and documents with dozens of macros & templates dropping them any time soon - they'll have to work harder to make sure those features/elements still work in an ODF doc. Time is money, and if they have to spend time on fixing something they'll just continue to use what works for them rather than spend more on the change than the supposed benefit of switching.
Biting the hand that feeds IT
