Im loving this new feature,
btw Not sure if this will be available or not in the upcoming production release, but i guess would be cool to be able to hide an opened window from the tabbed view list only. There are cases when there is the need to open a "shadow" window to do some stuff and for example we should prevent the user to close it by mistake from the mdi tabbed view, and in any case there's no need to show it listed. Would be cool a "hide in tabbed view" property accessible even by script.