Success - I've installed the USB driver and now the device is recognized and firmware updater runs fine.

I made the mistake of assuming if I'd installed the UFX driver, that I'd installed both USB and Firewire.  This is not the case.  In download section, choose the "USB" heading then the UFX driver package. 

To go into detail:  Funnily, all along I've understood that it requires USB, and thought I'd installed the USB driver but still the device was not being recognized, and that perhaps the firmware was too old to talk to the latest driver.  The problem was that I wrongly believed the "UFX Driver" I'd installed was universal:  Both firewire AND USB.  In retrospect, it seems obvious you'd want to be able to install the drivers independently, but my assumption was that when selecting "firewire" or "usb" on the downloads page, I was narrowing down on the hardware (UFX in my case) rather than narrowing down which connection method I wanted to install a driver for.  A confusion bred of assumptions meeting slightly unclear web design.

Perhaps you can consider adding a note to your documentation about this.  I'm sure it's crystal clear to anyone inside RME, or to any long-time users who are familiar w/ your approach.  However, to a new user it is a point of confusion. 

-jeremiah