When copying files to an iPod, rhythmbox silently creates duplicates (since the files will have different filenames, due to iPods screwed-up filesystem).

It should test if the (track)/title/artist/album combination already exists and if the file hashes are the same silently not copy the new file, if they are different, offer to overwrite the existing file or create a duplicate (like the old behaviour).

Also, this message should not appear as a dialog (like it's the case when you copy files from a DAAP-share that already exist locally: it stops the copying until you answered the question), but rather queue up while continuing to copy the files that need no questions answered. The queued-message dialog should also offer "for all" options.
(maybe this would be a good idea to build into rhythmbox as a new component? Like the "missing files" and "import errors", a new "questions" section?)