Ah, sorry. I mis-read.
I do all my updating/managing in Calibre and then when I download via opds I know its the latest. It would be convenient to allow overwriting on download.
I do use dropbox on occasion, and it is convenient, but I was worried about the reports that the admins scanned your files and shutdown accounts that had copyrighted works. I don't know if that is an issue anymore, but at the time that is why I set up the opds so I don't ever have to worry about someone else making me lose books I had purchased.
edit: Apparently they have figured out
their policy now, so they shouldn't shut down your account unless you have those items on shared folders.