I just love the indicator-applet and other parts of the Ayatana-project and think Ubuntu has done an awesome job there. And as the question about applet compatibility seem to be answered as a 'no' I'd like to take the question to the next level - the 'why' and 'why not'.
How come these Ayatana-applets today work in gnome-panel but gnome applets won't work in the Unity panel?
And - as it's connected - why not make them compatible? Isn't it all about usability?