I am on it now, using my iBook G4's keyboard and an external screen Booted from my firewire bootable backup of my iBook. I think I am going to use this to replace my server which is a 300 MHz clamshell. right now the powerbook only has 256MB ram, but I will throw 256 more in, and with a 550MHz G4 it will be awesome compared to the clamshell.
here is a picture