A vote from me as well for the cardbus!
My Firewire doesnt work at all, installed using the unsupported image install, which worked well in target disk install from a TiBook.
USB works great on all slots.
''unsupported usb device, click ok" prompt shows at every boot, unaware of how or what to use to silence that.
Also would share that these machines have major heat issues which can cause the lower ram slot and the ram itself to become defective. Spent several days diagnosing what i thought was an L2/L3 cache freezing. in both os 9 and OS X, but it turns out it was the lower ram slot all along (the one closest to battery). pitch the bad ram *whizzzzzzz*. I havent tested to see if the lower ram slot is permanently knackered.
Dropping the processor speed (which affects cache too) in the energy savings settings helps immensely with heat, but some of you might be doing more with the machine and in that case you can flip it over on your lunch break and cook an egg on the underside. Suprisingly working well at a crippled 666mhz! (devil hand emoji)