I just read Kims post about removing removing the default visibility of the menu and toolbar Working Set items. It triggered once again one thing that annoys me from time to time, the inflexibility of the Customize Perspective dialog:
You can either enable both, Menubar and Toolbar items or nothing. That is very annoying, because it breaks the principle that the toolbar items are optional. Unless the provider of the actionSet defines two action sets, one for the toolbar and one for the menubar, you have the choice between all or nothing.... But providing two action sets would duplicate the number of item on the command tab, which is already overloaded.
I think it is not the responsibility of the plugin writer to decide which items the user wants to see in the toolbar! (See bug 182714)