I feel very uncomfortable with Default torrent client called Transmission client which is available in most Linux distributions (i use fedora and ubuntu),It lacks some essential feature like option to shutdown the PC after the torrent Download. So I searched and found software called EasyShutdown which will automatically shutdown the PC after the set time in timer.
Using this software i will set the time for example 5 or 6 hour according to the remaining time to download the file(you can find this time in torrent client ).
You can Download this Application from Ubuntu launchpad as .deb file – Download Now
See some screenshots below :