It is most deadly on determining 1/2 ball shots, because that's the foundation of the system. Anyway, what it has done for me is help me focus on a specific aiming reference instead of just half-assing an appropriate aim.
With enough table time, as you already know, many shots become recognizable. As soon as you look at the shot you know exactly how to shoot it. But not all shots are this easy to recognize, and sometimes your mind pulls from memory something that is close to what you're looking at but not dead nuts on. That's where a system comes in handy as a double-check. Is it smart to reference such a system on every shot? Of course. But that requires creating the habit of doing so.