Bug 76969 Preference change not propegated.
build N20041024 - open the workbench - popup a menu over the perspective switcher and choose Dock On > Left NOTE that the UI does not respond right away (and it should). Seems that the listener is not being notified of the change.
bundles/org.eclipse.ui/src/org/eclipse/ui/internal/UIPreferenceInitializer.java
public void initializeDefaultPreferences() {
		IEclipsePreferences node = new DefaultScope().getNode(UIPlugin
				.getDefault().getBundle().getSymbolicName());
		node.put(IWorkbenchPreferenceConstants.OPEN_NEW_PERSPECTIVE,
				IWorkbenchPreferenceConstants.OPEN_PERSPECTIVE_REPLACE);
		
		node.put(IWorkbenchPreferenceConstants.PROJECT_OPEN_NEW_PERSPECTIVE,
				IWorkbenchPreferenceConstants.OPEN_PERSPECTIVE_REPLACE);
		node.put(IWorkbenchPreferenceConstants.SHIFT_OPEN_NEW_PERSPECTIVE,
				IWorkbenchPreferenceConstants.OPEN_PERSPECTIVE_REPLACE);
		node.put(IWorkbenchPreferenceConstants.ALTERNATE_OPEN_NEW_PERSPECTIVE,
				IWorkbenchPreferenceConstants.OPEN_PERSPECTIVE_REPLACE);
		
		
		
		
		
		node.putBoolean(IWorkbenchPreferenceConstants.LINK_NAVIGATOR_TO_EDITOR,