When visitors upload a file as attachement, I would bet many would come back and (along with other visitors) to see how many times their attachement was downloaded on a a simple "Top Downloads" page.
I think there could be a simple enough version that would just display already available informations (list all files/link to post; rank by # of d/l's, date, poster; filter by category/board).
Then this would ultimately open for a download center add-on (with transloading (url only), rates, description, moderation, etc.)...
Thoughts?
-- mrtn