I'm not crazy about them. True ghost ring sights can only function on rifles. This is because the closeness of the eye to the "ring" allows it to "ghost" out. This, in turn, allows the mind to subconsciously center the front sight post in the large aperture. This subconscious alignment is what makes GR sights so fast, while still providing good accuracy - the mind wants the eye to center things.
But now put this sight on a pistol that you hold at arm's length. Instead of looking through a giant (because it's close to the eye) hole, the eye must work to find a much, much smaller hole floating unsteadily somewhere out at arm's length. Compared to GR sights on a rifle, this is like threading a needle, and much slower without very extensive practice.
I have seen one outstanding shooter use GR sights on a revolver to very excellent effect. However, I think for most presbyopic people, things like laser sights, compact dot optics (like the Docter) and the Express Sights "Big Dot" are probably better solutions - at least if speed is a concern.