Yes, I use one a USB -> PS/2 adapter on mine.
I have the SlikStik illuminated balltop joys and if I plug my Ipac in with the USB cable, they are always on. I plug it into the PS/2 port and they go off when the machine is off.
Leaving the joys on to light up is cool...except when my little kids see them and start playing with the machine when I am not around.