As far as I know, it works Ken.
My laptop has both USB2 and USB3 and I've had no probs.
Can't verify with only USB3 machines though but I assume its the same.
I’ve just connected our iPad Air (IOS 9.1) to a native USB3 port on our Desk Top PC (Win 7 Pro) and iTunes (12.2.1.23) launched and the iPad synced with no problems.