I was just wondering if the speed limitation for Time Machine is the interface, or Time Machine itself? I am thinking of getting a 750 GB Iomega external hard drive: http://store.apple.com/us/product/TQ587ZM/A?fnode=home/shop_mac/mac_accessories/storage&mco=MTQ2NDc5 But, I read some reviews saying it was slow. Is that because the drive is slow, USB 2.0 is slow or Time Machine is slow? Is Firewire 400 faster? Is the Iomega an OK drive to get?