If skeuomorphism is helpful, it's not generally because it gives familiarity with specific controls—we've all dealt with frustrating virtual knobs. It's that it gives a "face" (or, if you'd prefer, a "brand") to an app, which for some makes it more approachable. Lack of user confidence is often a major usability issue.
Also, and perhaps more importantly, it can visually differentiate sections within the app, making it easier to navigate and feel comfortable with the app's modes of operation. Users often get lost within a maze of twisty dialog boxes all alike. The real world tends to have many visual cues and context indicators that help people mentally build and organize hierarchies — for me, at least, it’s hugely easier to remember people if I have an image to associate with that string, i.e. a face to put with that name.
If skeuomorphism is helpful, it's not generally because it gives familiarity with specific controls—we've all dealt with frustrating virtual knobs. It's that it gives a "face" (or, if you'd prefer, a "brand") to an app, which for some makes it more approachable. Lack of user confidence is often a major usability issue.
Also, and perhaps more importantly, it can visually differentiate sections within the app, making it easier to navigate and feel comfortable with the app's modes of operation. Users often get lost within a maze of twisty dialog boxes all alike. The real world tends to have many visual cues and context indicators that help people mentally build and organize hierarchies — for me, at least, it’s hugely easier to remember people if I have an image to associate with that string, i.e. a face to put with that name.