I like to talk periodically about how you actually do the work of migrating your systems, and your users, to OpenOffice.org. Even better, I like to find other people's advice on how to do this. Bob Sutor has an excellent list of questions to ask. Once you have the answers, you can start in on the plan. His list, 10 possible elements of your ODF migration strategy, has a lot in common with my own recommendations, including identifying gurus to start working on the migration.
Based on my own experience, I want to strongly recommend among other things that if you have complex or badly formatted documents that are causing problems when you convert, just pay to get them converted. Your users will be far happier.