Control center doesn't work as well on light backgrounds as it did in beta 6. Before it used to dim on a light background so you could see the white elements. In the GM, the background still dims above the control center panel, but the panel itself stays the same brightness. I have no explanation for this change except that someone at Apple goofed. It was working fine in every previous beta. Also, the amount of transparency seems like it has been reduced as we'll throughout the OS. See the attached screenshot.
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I can see why they made this change. In order for you to be able to adjust the brightness of your iPad, you need to be able to see how bright it is as you move the slider. If everything gets dimmed, you can't tell how bright it is.