QLDP implements a graphical user interface on the QUAKE LIVE website itself. This GUI helps you playback your demo files. It lets you filter demos by type, players, maps and/or date and time. It also lets you sort by the same columns previously mentioned.
It also generated a playlist and launches the QUAKE LIVE client for you, and implements some small functionality into the client itself, such as the commands 'vstr next-demo' and 'vstr prev-demo' which will let you skip back and forward through your playlist.