Go vote on this bug
Firefox (and all other browsers I know) are missing a feature that I would find really useful when I upload stuff via a HTML form: How much longer will it take? There is no progress bar with an ETA. There is a bug about this on bugzilla, and I’d like you to go vote for it. Maybe if you are a c++ god and have some time you could make a patch.
Me? C++ would explode my brain (I know I’ve tried).