I have found the usb on the sam with os4.1 on the whole to be pretty good. The worst thing is the lack of usb2 of course. Other than that the only problem I've had is sometimes I loose my saitek mouse. I'm going to try a different one, see if it ever happens with that one. It doesn't happen often enough to be a real pain.
On a related subject does anyone have experience of a card reader that works well under os4.1? I use an 8gb Micro SD HC card in my phone I'd like to be able to access.