Once the plugin is installed, the download can start automaticly when you open a download webpage.
This makes user experience a lot better.
Of course, you upload data only when you are downloading or the plugin is visible : when you stop the download windows, you stop uploading.

Here is a demo link :
http://www.peerfactor.fr/getdownload.jsp?ID=110
With Media player on IE : http://peerfactor.fr/mediaplayer.htm

What's next ?
1) In begin of october, new release with a new P2P engine.
2) And after, P2P Streaming