For as long as I've been using Media Center (since the first betas in early spring of 2002), I've always been annoyed at the transport control toolbar, and the actions that prompt it to appear.
In Media Center revisions prior to Vista, the transport control toolbar looked like the highlighted area in the picture below.
As you can see, the old transport control bar would block out tickers completely, and other on-screen elements of the tv shows that you are watching.
For Vista, they have made some changes to improve this. Here is a screenshot of what the transport control bar looks like in Beta 2 of Vista.
As you can see, the transport control bar is much less obtrusive, and is actually slightly transparent, so you can see content underneath it.
Now that they have improved this aspect of the transport control toolbar, I would like to focus on the second annoying behaviour that I've encountered. Right now, when there is ANY mouse action over the Media Center application (whether Media Center is in full screen or windowed mode), the transport control toolbar will show up. I've made a suggestion that the transport control toolbar appear only if I actually click on the mouse while it is over the Media Center application. Why? I'm someone who typically runs Media Center in windowed mode on my desktop while I do other things in the background (such as writing blog entries, replying to e-mails and newsgroup posts etc). As it stands now, if I move my mouse over the Media Center window, my content that I'm viewing gets blocked. Unfortunately, my idea seems to have been passed over. What suggestions do you have to make this a better user experience for people? I'd definitely be open to suggestions to bring forward to the product team.