This is an IDEA...
IF there is enough interest I will prototype this idea and pass it on to the GTK/QT/KDE guys as it would require new features to be made available in the toolkits for applications to use.
The idea is that the menu entries have different colours and font styles depending on function.
Say file operations are blue, help is green, dengerious functions are red and italic.
The greatest usability improvement comes when menu entries relating to the currently selected object are coloured.
Imagine using a version of gimp that highlights menu entries that are related to the tool in use, or a version of kword that highlights formatting menu entries when a block of text is selected etc....
This should help flatten the learning curve of new users and those users switching application of changing over from windows.
The mockup isn't that great, bolding some entries would help and don't forget this is going to change on the fly so it should be more obvious than the mockup shows.