Migrating from Office Communicator to Ignite

I will be doing a complete migration from Office Communicator to Ignite Realtime in the next few days. I’d like to make the process as seamless as possible for the users. Has anyone ever done a similar migration? My main concern is moving the users buddy lists from Office Communicator back into their Spark clients. This will be an Active Directory integrated installation of Ignite Realtime running on CentOS 6.3.

Any advice, pointers etc, would be greatly appreciated!