Just in case you missed it buried underneath the upgrade to Netflix Watch Instantly the other day, Microsoft has gone live with Internet TV on Windows 7 Media Center, offering content (of rather poor picture quality) from the following providers:
FINALLY. Microsoft and CableLabs are finally opened the door to have regular people add in CableCARD tuners by themselves, after they've purchased the PC and set it up. This is good news.
One advantage Windows 7 has over OS X is that you can stream to your Xbox 360 without the need for third-party software. And though it's still rough around the edges, it mostly functions.