The Classic Controller widget that was available in beta, was removed from the ArcGIS Viewer for Flex final release, because a lot of the user feedback we received indicated that it wasn't really a "nice looking" UI. Many said the Header Controller widget was a major improvement in terms of UI design.
During beta, the Classic Controller widget had the advantage of being able to group widgets into dropdown menus. This is now possible in the Header Controller widget by using a <widgetgroup> tag in the <widgetcontainer> tag.
thanks Derek, I did not know about widgetgroups. Very nice! This leads to my next question. I see widgetgroup has an icon property, but I don't seem to be able to change it. Do they have a sample somewhere?