Ribbon UI is very discoverable. I bet most people would have a better chance of picking up a feature-rich program such as AutoCAD nowadays than back in the time

Ribbon UI is very discoverable. I bet most people would have a better chance of picking up a feature-rich program such as AutoCAD nowadays than back in the time of menus and toolbars. CAD packages are a good example, really. They tend to have tons of features, which are fairly easy to find with a ribbon, but also have lots of configurability (hideable toolbars) and speed features (radial menus) for power users. But the balance is hard to strike - if anything they tend to have too many ways of doing things, and not good enough defaults. The current incarnation of Microsoft Office products' UI is a mess too. Buttons and search bars all over the chrome of the windows (what used to be the title bar), most of the old Alt+letter codes still working, and ribbon 'tabs' that bring up full-page menus (the File menu). My answer to your probably-rhetorical question is yes, you should use a ribbon design in a windowed app, to provide a baseline level of making the features easy-to-find. The difficult part is adding more powerful power-user features or most-used features without turning the interface into a big mess.