tglEdgeHardness.mel is best used on a hotkey to toggle between hard and smooth normals on a selected object. It stores information about the object- like the last toggle state and the name of the polySoftEdge node- to insure that only one polySoftEdge node is created. If you delete history on an object and run the toggle it will create a new polySoftNode.

This may work on much older versions of maya, though it hasn't been tested on anything but Windows Maya Unlimited 6.5.

Note: If it is not working, your normals may be locked. Go to "Edit Polygons>Normals>Set Vertex Normal" and check "Unlock Normals."

-Shawn Lipowski
www.lickmypixel.com