@AusPPC

The numbers in MUIM_Notify are explained here, anyway I see you've got it right .

I prefer the intuition style event loop and to avoid the use of hooks.

Indeed hooks are old style and not recommended in general. The proper way is to subclass and use own methods, as described here and shown in the SciMark2 example. Intuition style event loop can be done with MUIA_Application_ReturnID, but it is considered bad style, for several reasons.

Is a MUI window object pointer the same as a window handle?

No. If you really need Intuition window handle, use macro _window(obj), where obj is MUI window object pointer. Anyway trying to bypass MUI user input handling is entering a minefield...

Can I get Intuimessages from an MUI window containing MUI buttons / gadgets?

It is usually done for custom gadgets derived from Area class, by implementing MUIM_HandleEvent() method. Usually when one uses only standard classes, MUI handless intuimessages by itself. If you need some timed events it may be good to use timer.device directly (depends on application).