One of the coolest settings on the F100, IMO, is #4.
When set to disabled, 1, the shutter trigger button no longer triggers autofocus. Instead you have to Autofocus with the AF button on the back which is virtually under your thumb when holding the camera.
I combine that with custom setting 7 enabled, 1, which makes a half push of the shutter button lock the exposure setting.
Nine is set to, 1, disabled.
Ten is set to, 0, disabled.
These settings allow me to pick my exposure in one place (push and hold), pick my focus point in another (push and release), then I can reframe and shoot where I please almost as if it were (for that moment) a fully manual camera.
That ability is why I own an F100 and an F5. It makes life easier for a guy with old eyes.