It was as easy to use as an official streaming service is, with integrated subtitles downloads in the background (from open subtitles), links to trailers and critics sites (it also pulled a lot of metadata from different sources).

Popular movies were always on top of the list because the default sorting was by seeders and these movies would load instantly

At the time it was the best streaming experience existing, paid or free combined.

[edit] oh and install was just dropping an all-in-one app somewhere on your computer and launch it.

Why "was" ?

Mostly the GUI, which is reminiscent of Netflix, and also the torrent client config. You hit play button on a video poster image, client sequentially downloads blocks of videos until the buffer outruns the download rate (this is the main difference from other clients which can’t/don’t download blocks sequentially), then it autoplays, pausing for more buffering if needed, with one click.