Backrow, the GUI that is used with the Apple TV was quickly spotted to have a plugin architecture, intended to allow for it to be extended and improved. Apple have provided no documentation or details about this, but it has been successfully reverse engineered to the point where some plugins have been made. Thanks go to XianLi over at hackint0sh.org for the tip off.
You can download a “Quit” plugin here which provide an option to quit BackRow, and thus if you are using it as a front end on top of regular OS X, you can use it and drop back out to the OS to use other apps or media apps.
Once downloaded, unzip it and copy Quit.frappliance inside the plugin folder located here:
Make your own
For the programmers amongst you, there is a tutorial on creating plugins over at the excellent Awkward TV wiki.