This Firewire is FW400 which runs at 400Mbps rather than USB 1.1 which runs at 12Mbps.
If you are connecting an external drive, make sure it has a FW connector.
The hardware does not support USB 2.0. Add a USB 2.0 external hub and it still runs at USB 1.1 at the iBook connector.
In order of speed (lowest first)
USB 1.0 -> USB 1.1 -> FW400 -> USB 2.0 -> FW800
1Mbps -> 12Mbps -> 400Mbps -> 480Mbps -> 800Mbps
But in the best tradition of all of these standards, YMMV.