I just did an in-place upgrade over top my Windows 7 Ultimate setup with Windows 8 Pro. After doing the upgrade, I immediately used the free coupon to get Media Center back (since the upgrade helpfully takes media center away from you).
Well, after 3 restarts, Media Center was back. I loaded it up and it said it detected a previous MC config and asked if I wanted to import. Hell yes I did. After it was done, TV was working perfectly again.
Now, the kicker (or bummer) - i dragged the window over to the displayport connected screen and it MC window popped up and said it needed an update (it basically said to go to windows update and install an optional update there). When I went, the only thing there remotely close was
http://support.microsoft.com/kb/2712101Edit: installed the update and now all it does is give the same message as Windows 7 did: "Display driver error: the video playback device does not support playback of protected content."
Oh, and one more thing. After Windows 8 removed Media Center and I had to get it back installed, there literally are zero differences that i've found thus far. Sad, very sad.