Initially, I got the problem that almost everything I plugged in freezed AROS. Moreover, I couldn't mount any USB 2 device, because they were totally ignored by the system. So, I decided to peek the BIOS settings and I've spotted two meaning options:
USB Controller (enabled)
USB Legacy Support (enabled)
Since I remember that Legacy Support may be annoying for USB drivers, I disabled it and I could go further. The USB universal card reader connected to my mobo came to life and I could at least mount compact flash cards formatted by my digital camera (now I need a good .orf reader for AROS...), while SD cards are still a issue. I could even connect USB 2.0 pendrives, although AROS couldn't mount them because - for some reasons - it doesn't support FAT32 properly. Thinier USB pendrives of 128 MB or so worked, however. But the most incredible oddity I could find with this release was the "locked" support for 1.1 devices: I couldn't use anything slower, from mice to keyboards, just because they weren't even recognized, due to some not better specified "eletric problems" that intercurred between the devices, the SB600 southbridge and Poseidon. This problem continued until I connected a Microsoft Xbox360 Controller for Windows, the PC version of the Xbox 360 gamepad. This time, Poseidon reacted in a different way finding a "controller" and, after that, I could connect ANY USB device that it would be at least correctly recognized.
So, for now, when I need to test a USB device I do like this: I turn on my computer, plug in the Microsoft Xbox 360 controller for Windows, unplug it, and then I can connect anything I want. I wouldn't ever imagined that a gamepad from Bill Gates would be the key to respawn all my USB devices. And no, I won't sell or give my precious Xbox controller to anyone. ;-)
Please, help us with beta testing if you can, because the more Poseidon will be tested by users, the faster it will be perfectly functional for everyone!