First of all; thanks for a wonderful product! I just love it, and it makes my friends strongly consider Linux over Windows!!
I have added torrentflux to my LinuxMCE box. It's a great torrent php client (using bittornado as back-end.. if I am not wrong).
It's included in the kubuntu repository, but I think it should be preinstalled in LinuxMCE, as most of us do download torrents every now and again.
Here's the website: http://www.torrentflux.com