One of the main issues is the somewhat broken F-KEY access which makes F1-F6 almost unusable.
It seems there are two options to change the F-KEY behaviour: Either boot to OS 9 and change the behaviour of the fn key in the keyboard control panel or use http://www.gnufoo.org/ucontrol.
-- JensSchumann - 18 Mar 2003
OS X 10.3 allows you to turn the Function Keys back on.
-- ChrisHibbert - 03 May 2004