I would be interested in any user's opinions on a Fuji GX680I or II vs the GX680III. From what I can gather there are two differences - the battery used and data imprinting by the film back. Am I missing something else that would be important? The body style is also a little different, is that something that would make a difference? Are the accessories interchangeable between the models? Also, there seems to be an extra "data" port on the III's body below the remote release port - what is that used for?