well, it was working fine until recently. and even now with problems, occationlly the flash drive can be detected and used normaly, once detected, never had a problem transfering data from or to the flash drive.
i have no idea what triggers the problem, whether it can be detected by the system seems random, except when i leave the drive in the usb port and reboot, it gets detected every time.
so Surface RT should have no problem with USB 3.0 devices, at leaset until recently.