Just bought an Extreme today and am getting it setup. The drive I have connected is a 3TB Seagate. I have an iMac and a MB Pro. What I want to do is use the drive for Time machine backups of both machines. I also would like to to move my iTunes library to it and share it between both machines. I told the lady at the Apple Store that this is my plan and she said it would work but I am having some intermittent success. Backups do not always work and I can not get iTunes to publish my library to the iMac.