As part of the new tech setup, I've been working on getting my mythtv PC to work with HDTV. That shouldn't be hard in theory, but "theory, theory and practise are the same, in practise, they're not :)".
The first thing I found out is that the AMD Sempron 3100+ CPU in there isn't fast enough to play even 720p in realtime, but I found that by using nvidia's XvMC in the card, that was good enough to barely play HDTV in realtime (although that took some configuring).
Then came the problem of actually recording HD content: I had gotten an HDHomeRun from a coworker, which is indeed a neat little device that records unencrypted HD from cable, and forwards the mpeg2 stream to a computer, in my case my mythtv computer.
Up to then, my cable quality was an issue in the house because the incoming cable feed was split 2 ways outside by comcast, then 6 ways to each rooms, and then another 8 ways next to my my AV center in the family room. Obviously the signal was crap by then and I had to find places where to put amps and where to split the signal just the right amount of times.
I found a good store close to my house where they had all kinds of home wiring stuff, including various amps and high quality splitters, and after that the fun was to find where to put the amps, splitters, and signal attenuators (yes, ampping too much makes things not work) to get everything to work. Oh, the best part is that if you put a cable modem behind a regular amp, it won't work, you need a 2 way amp for the return signal of the cable modem to work.
Anyway, when half a day later I had decent analog cable signal where I needed to, I was able to get unencrypted HDTV channels to both my TVs and especially the HDHomeRun device.
You'd think I'd be done by then, but that didn't do much good until mythtv both had TV guide data for the HD channels, and knew to prefer HD recordings to regular recordings. That part wasn't much documented but I got help on the mythtv-users list , which basically was a matter of finding the right xmlids for the HD channels and giving them a higher priority over the same channels.
Anyway, after all this, I finally got one program in my lineup that recorded in HD: the weekly episode of ER, which was a nice surprise.
Yet, for SciFi-HD, I still get to download shows from BT if I want HD because comcast suck (and if they didn't suck, it'd be encrypted so that I can't get it anyway...).
Some people would ask why I go through this pain, which is a valid question. I still like the flexibility of running my DVR, as well as the occasional tinkering.