I have tried Girder to implement global hot keys controlling Media Center while using another program, but I have found some difficulties. It is so essential to have real-time access to Media Center features, while the program natively supports most of its functions with two, three or four mouse clicks. Not a so real-time interaction, really.
I devised a combination of Win key plus Numeric Keypad keys as suitable shortcuts. But when I press a Win+Keypad key combination, Girder correctly intercepts the entire key combination, while the currently active program intercepts the Keypad key alone (without the Win modifier), and acts accordingly. So I get a beep or, worse, unexpected behaviour. So I have to find a way to quickly discard the key combination from the buffer in Girder, preventing it to go to the currently running program too, or devise other combinations, for example Ctrl+Alt+Win+Keypad key.
Also, Girder communicates with Media Center by launching an executable, mjextman.exe (Media Jukebox Command line parameters
http://www.musicex.com/mediajukebox/DevZone/CommandLine.html). Really slow, no real-time response. There is also a little documented opportunity to send Windows commands (signals) from another application directly to Media Center (Media Core Command List
http://www.musicex.com/mediacenter/DevZone/MCCommands.h). I have tried sending those signals directly from Girder with no success (I am no Girder expert). Maybe you have to send them using mjextman.exe, but the benefits of sending command directly, without loading an executable from hard disk, would be lost.
After I found those difficulties, I have stopped experimenting with Girder and Media Center. I will keep you updated when I try again.
By, the way, wouldn't it be nice to see the title of the current playing track in the title bar of the active window? Is there any plug-in that does just that?