While the RB menu will open as always, Front Row renders its UI in 
such a way that no other application is able to render their window/ 
content on top. So you could still use Remote Buddy's menu "blindly", 
but I don't see too much use in that.

Regarding the rating: the rating continues to change the rating of the 
current song in iTunes. Due to the changes in Front Row, you won't be 
able to see the menu, though nor will you be able to change the rating 
of the current song in Front Row. Front Row now is independant from 
iTunes whereas previous versions depended on it for playback.

Best regards, 
Felix