I had a little bit of trouble, but I think it can be attributed to the PC partially recognizing the device somehow, throwing off the upgrade mode. Try just making sure the device is switched off and unplugged from the PC each time you try it ... if it boots up all the way (fails to go into upgrade mode) you won't get it to work until you unplug it from the USB, switch it off, and then plug it back in before trying again. (At least, that seemed to work for me.)

P.S. Oh, and I successfully updated in R&D mode. It was still in R&D mode after the update.