I'm not a usb expert, but have done some hacking on it and
have been tempted (a few times) to clean up a bit the
usbd/drivers/#U relationship. We are also running for usb 2.0
devices, and have some of them around, including a touch screen.
BTW, the specs in the usb web site are pretty complete.

It would be great if you could Cc me any mail regarding this issue,
I might help.