mceZone have released a beta of their Twitter addin for Windows Media Center, I don’t have the details on what has changed but I installed the new version and had a play and I have to say it looks great. You can view your timeline, see your replies and send out tweets. If your watching TV the app overlays over the video playback which is a nice feature.
The app is a free but there is a 15 second delay when it starts, if you donate via paypal the message is removed.
All in all its a nice addin if your into Twitter and you want to see it on your TV