Horrible.
I'm puzzled if this was even tested.
The idea of having two layers of controls in one button (settings and the click to shoot) is really odd.
I watched the Apple event, and how you are supposed to use it, but there is a big issue:
The button is too stiff. The people who designed it, never used a real camera.
The shutter button is the most delicate and soft to press button in any camera to avoid blurred pictures.
What's my experience with Camera Control?
When I launch the camera and I'm ready to shoot, a slight movement of the finger over the button is enough to launch the settings. This happens even when I in the process of depress the button to click it.
Then, any other finger movement will change your settings (whatever is open, camera, zoo, exposure) perfectly ruining your shoot.
Disabling the settings part of it, and it's still too stiff to avoid phone movement while using it.
And I'm even more puzzled by the incoming software update that will add half-press to focus...that will be a third layer of controls in one button.
The only thing that can make it usable is to add a second button next to it. A real soft-shutter button.
And use the Camera Control just for settings.