Oh, even though I don't use one there are several advantages to a Hamilton Quick Action. If they used the same stiffness of rubber as a shubb (the standard bodge for this back in the 60s and 70s was to use the rubber gas pipe from a bunsen burner) then there is no reason for them to pull a guitar out of tune more than a shubb, and indeed they cannot produce the vice-like clamping effect of a shubb which almost always pulls a guitar out of tune, they don't need you to adjust a screw every time you move the capo up or down the neck, they don't have the shubb's tendency to be tighter on one side of the neck or the other, and they canbe slid one way (usually up) the neck one handed quite easily and IMHO more easily than a shubb.