I have both the ATV 1 and 2, both with ATV flash on them.
The ATV1 though seems to have stopped playing with our NAS drive. Using XBMC the drive mounts Ok but I just get a message saying no contents shared. It works just fine on ATV2.
P.S Is there an issue with LION and ATV syncing? Since upgrading I have been unable to see my ATV1 in itunes.