Seriously … i do not understand why everyone cries for this. I can understand the point of showing some progressbar for long running uploads.
But… the browser already has all needed informations. it knows the original size. it knows how much data was sent already. We could do the whole calculation fully client side. Now what are we doing? We waste a 2nd connection to poll the webserver “how much data did i send to you already?”. This feels stupid to me.