So what does all this changing around give us.
1. It gives us the ability to have the GUI abstacted away from the plugin. This is good in that then the GUI will not conflict with the GUI of the browser. So now Opera and perhaps Konqueror can become fully supported again.
2. This also gives gecko-mediaplayer the ability to use different players as long as they emulate that gnome-mplayer dbus interface.
All in all I think it is a good change. I think the code will be easier to maintain and therefore should be more reliable.
Edit 2010/02/22: Updated Links