Just to bump this old thread of mine, I finally got around to digging out a spare CF card and formatting it with nothing but Workbench 3.1, MUI, and the Poseidon USB stack. Booting off that I was able to get a generic USB keyboard to work, but not a mouse. The mouse was detected but if I tried to move it the pointer would just disappear. The keyboard worked okay, but was a bit sluggish. Not really sure what else I can do with the card at this point, but would be interested in hearing if anyone else has managed to get one working properly in an A2000? Seems my 040 just doesn't have the oomph, or it's the ZII bus. I suspect most users are on A3000/A4000...
Anyone know where I can track down a copy of the original Thylacine disk? The link on amiga.resource.cx for Thylacine1.3.lha is dead. Might give that a shot and skip Poseidon, see if I have any better luck.
Also FYI the guy building them on Amibay is now starting to take pre-orders for a four-port version. Not cheap though!