If I understood the intention correctly, it's not about saving time downloading files when saving them from the internet to your computer or Dropbox, it's really about saving the time you spend uploading large files that you downloaded from the internet from your computer to your Dropbox. At least where I live the upload speeds on normal internet connections are way smaller than the download speeds, so what this app basically does (I think) is download the file to your Dropbox via their server, so you don't have to spend the time uploading the huge file to Dropbox because those guys did that part for you.