I'm a recent iPad owner, I've only run iOS 4.2. I know the slider switch is supposed to be a mute, and indeed it does paint a pretty icon that seems to indicate no volume. However, it doesn't actually do anything. Should it? I can't figure out what auto-brightness actually does. I see an extremely slight change when I toggle it on and off, but the manual setting is still active and actually changes the brightness no matter the auto setting. Does auto brightness do anything? Thanks.