The above is basically just a little progress bar along the top of the browser window, telling the users that somethings happening and given the current speed / progress when it might be done.
We actually had a need for exactly this on a new multi file uploader we have been working on. It works really nicely.
Could be miss used very easily and hurt UX, but i think in our case, its just nice, will see what our users thing soon enough!
via hacker news https://news.ycombinator.com/item?id=6246183