Thomas Hawk has an excellent writeup on his blogger's dinner with Microsoft VP Jim Allchin last week. Jim confirmed that in order to get HDTV over digital cable in a Windows Vista PC, you'll have to buy a PC system that has been "certified" by CableLabs. Unfortunately there's nothing Microsoft could do here - they must honor the wishes of CableLabs. I've been fortunate to be one of those who has been testing the technology and I have to say it's fantastic. I've done A/B switching tests vs. my Comcast set-top DVR and see no difference in image quality, despite the fact that the tuner is a simple USB-based box (RNDIS) that you just plug your cable (and cable card) into and go. No news on whether free and clear QAM services will require a CableLabs certified system but I will check. I suspect local channels in HD may still be an often from after-market or home grown builders. In order to get your premium channels DVR'd you'll need that CableCard-qualified system and CableCard installed by your local cable operator.
Also news at CES was the DirecTV Media Center announcement. In the future (timing wasn't discussed), you'll be able to have an installer come out and install a DirecTV tuner into your Media Center PC and get your local channels complete with DVR. As many know, DirecTV uses their own protection scheme with a "conditional access card" not unlike a cablecard. The big difference here is that they recognize the value in offering an after-market system installed by their own installers. In the past, it was DirecTV that was considered "evil" for their use of DRM and protecting their assets too stringently vs. Cable. Could the shoe be on the other foot? Only time will tell.
Disclaimer The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.