Originally Posted by sweeks

You may be right. I've always thought that the resistance to sliding (sideways) is limited by the shear strength of the ice, which I believe is greater at lower temperatures. There's no doubt that the grip afforded by studs, regardless of number ("density") or wear status, is considerably less than rubber on dry pavement. You can't just lay the bike into a high-speed curve. But straight-line travel and careful turns are much more predictable with studs.
That lake in the picture is nicely frozen over with no snow cover! I'm mounting those Nokians and planning a ride tomorrow. I'll see if I can calibrate myself on the hard ice so I can compare with softer stuff when the weather warms up.