I use Linux Mint with XBMC on my HTPC, and I have a downloader box running SickBeard/CouchPotato/SABnzbd on Ubuntu. I don't really watch live TV, but I do have a HDHomerun dual tuner on my network that I'm not really using. I understand that I can drive it with MythTV backend and there is a frontend add-on for XBMC for live TV, but I haven't been suitably motivated to get it working.
In the past I had run MythTV frontend and backend which did DVR and commercial flagging, but since the digital transition the number of unencrypted channels dropped drastically.
All I'd really be interested in for live TV would be sporting events, so I may eventually get around to getting the HDhomerun active again.