Getting back to the topic (sorry we got carried far away to sideline) I think notification system is one of strong points in MUI API. You can add callback hooks and methods to events so you dont have to mess with this in your event loop. It also allows simple automation of events i.e. when user presses a button MUI could automatically window title for example.
Another difference in MUI is that you can define window or context menus as objects. You dont necessarily have to define static menu structure (but you can if you want to). They can be used to store attributes and they are part of notification system so menu selections can be automated just like everything else. You can expand and shrink menus simply by adding or removing objects from them.