Discoverability != usability. Products designed for casual, first-time users must be discoverable (= it's easy to figure out how to do things), while tools for

Discoverability != usability. Products designed for casual, first-time users must be discoverable (= it's easy to figure out how to do things), while tools for professionals repeating a workflow over and over must be usable (= fast to do what you want). Photoshop is usable but not discoverable, Gmail has to be both and it's a fine line to walk.