just to make an example I could see that the USB support is done and working, also on the A4000: the A4000 had 2 keyboards and 2 mouse connected, the regualar Amiga keyboard and mouse, and an USB keyboard and mouse, and you could use them simultaneously, i.e. type at the same time on both keyboards and use both mouses.
Wow, thanks for such a detailed report. That keyboard/mouse configuration is something that I suggested as a cool feature to add (not to say I'm responsible) years ago during my days on Compuserve. We were discussing things we'd like to see in upcoming AmigaOS versions and that was something I wanted. For instance, to have multiplayer games with one system and each could have their own keyboard and mouse. That would be so cool. I could think of other uses as well.