I often collaborate with others using shared folders containing 100s of small-medium sized files, and I'd love it if I could subscribe to a notification that alerts me when a synchronisation to Dropbox is complete. As it is currently, I'm forced to check the Dropbox icon periodically to check "is it done yet?" in order to find out if the sync has completed.
E.g. I save my work into my Dropbox, sync starts automatically. From the Dropbox menu, select "Alert me when sync is complete". That way I can walk away, forget about it and have Dropbox let me know when my files are ready for my collaborators via an alert of some description that must be clicked off of the screen.