The visual representation of the switch widget for iOS 1-4 was ambiguous because the width of the draggable knob was about half of the overall width of the widget. When you look at it, it isn’t immediately clear whether the blue part is meant to signify the knob. Its new design in iOS 5 appears to have resolved this ambiguity by making the knob much narrower, and circular rather than rectangular. I really like it. Plus, the rounded corners better conform to the overall look and feel of iOS.