Has anyone owned/used a Contax D9 databack for the Aria?

Just curious, as it sounds like it would be a great accessory, in part because of the between-the-frames or end-of-film printing of exposure data. But I've only ever seen one -- quasi-busted -- for sale online, so they seem to be quite rare. If you've used one, I'd be interested to read your thoughts on its utility and ease (?) of operation.

I guess the lack of response indicates just how uncommon this thing is!