According to a note just posted at SuperSiteBlog:
the version of Windows Media Center in Windows 7 has gotten a significant update today, with the addition of Netflix and a new version of the Internet TV functionality, the latter of which has all kinds of new content, including great TV shows, Zune video podcasts, and more. It's an excellent update, from what I can tell so far, and I will have a short, more formal write-up about this later in the week. Check it out if you're using Windows 7!
Wow! That’s really good news! I have a Roku box at home for Netflix but lately I have been playing most of the time with 7MC (Windows 7 Media Center) using a Ruvo mini PC and I have been waiting for this update. I really want to see how Netflix works within 7MC. A friend of mine just tried Windows Update and did not find anything so let’s hope that tonight this new update is finally released to everybody.