GUIs have a nice ramp-up and a fixed ceiling, whereas command lines require you to climb a brick wall (the part where you learn enough commands to make it worth

GUIs have a nice ramp-up and a fixed ceiling, whereas command lines require you to climb a brick wall (the part where you learn enough commands to make it worthwhile, pretty much by rote) but, as long as they're scriptable, the ceiling is close to unlimited. (TUIs are, or can be, GUIs with box drawing characters instead of pixel displays. They're not necessarily any more scriptable or any less discoverable; however, a TUI on top of a command line, like Norton Commander or Midnight Commander, can be a real winner of a design paradigm.)