Boxee does internet TV.. on demand TV. I've been using it since Linux-alpha. I'm not in love with it per-se but it works in an amazing fashion. It brings me all of the shows I watch regularly on demand. No PVR no recording.
The home security part of this system makes me want to use it not the PVR. It's actually tough to give up Boxee. Though it looks like this is the way to go, for home security without a lot of work.