I couldn't find this information anywhere on the Internet, so I thought I'd post it here in case it can be of help to someone.
As of April 29, 2011, after applying the current firmware update
, my 609 reports its firmware version as 1031-0400-0010-3101
By the way, I tried doing the firmware update over the network and ended up with Error!! 3-84
on the display. I was afraid I'd bricked it, but after unplugging and replugging it came back to life. I had no problem with the update over USB -- let's hope that one of the things fixed by the firmware update is the network firmware update process!