thats true the g4 minis dont have gigabit, but with 10.5 screensharing-host is still brillant. - almost no difference to my intel minis which are 4 times faster (at least when you use a smaller window, in 1920x1200 fullscreen the g4 has no chance against the core2duo.)
kdx lacks full keyboard support, screensharing lacks multiclient functions and doesn remeber window size, and all proper solutions like evovia screen4 will require 10.7 and lack OS9 and windows support.
tumbuktu sucks - i have been recommended to try teamviewer... for a mixed network with one client - my last chance, or i have to give up 10.4.11 as client (which would suck)