I have been using SageTV and their Media Extenders for a couple of years now, and I am very happy with it.
The basics:
1) You set up a "server" PC loaded with hard drives and tuner/capture cards, running the SageTV software.
2) At the TV, you connect a small, low-power Media Extender, which presents an identical user interface to the SageTV software.
I am using this to record broadcast TV from an antenna, watch DVD and Blu-ray rips, and (with the addition of PlayOn) watch Hulu and Comedy Central streaming.
Their website: http://sagetv.com/
I used to use MythTV, and I find that SageTV has pretty much identical functionality, but I could remove a computer from the living room and use the small extender device instead.
Numeric stability is probably not all that important when you're guessing.