--allow certain upload folders to get preferred status in upload slots (reserving upload slots for certain folder access). i.e., anyone requesting myprecious.jpg never has to wait for an upload slot.
--sharing of portions of iTunes selections by choosing a playlist
--multiple download folders organized by file type

Sam, as we talked recently about a needed killer feature for XYZ, this is IMO one.

--an Edit menu! (and ability to select and copy any displayed text.)

Not to mention the shortcuts for the Menu Items.