The state of items in the segmented "Features" toolbar control is not readily apparent in Mac OS X 10.5.1 ("Leopard"), presumably due to visual changes introduced by Apple in 10.5.
For example, when the "Wireframe" button at the left of the control is clicked, the button's appearance does not remain "active" after you release the mouse to indicate that wireframe mode is on. In Mac OS X 10.4 ("Tiger"), the active state is indicated by a blue background.
In contrast, the View Mode control - with mutually exclusive items - does indicate the selected item with a "pressed" appearance.
These observations were made with LDView 3.3 Pre-Alpha, built from CVS around November 21, 2007.