As a result of a recent article I did for Handguns Magazine on upgrading Glocks, I ended up corresponding with a reader, and he sent me a picture of his personal carry gun. He had replaced the factory sights with an aftermarket set he really liked. I'm all for personalizing guns so they are easier to shoot (cars come with tilting steering wheels and adjustable seats for a reason), and factory plastic Glock sights leave a lot to be desired, but I was surprised to see that he had ghost ring sights on his pistol. I didn't even know they still made ghost ring sights for pistols.
I don't know if Jeff Cooper coined the term "ghost ring", but he popularized its use, and he advocated the use of ghost ring sights on shotguns and dangerous game bolt action rifles. I read all about them during my formative years (when I was old enough to buy gun magazines, but not guns).
What's a ghost ring sight? Pair the front sight of your choice with an aperture rear, and not a small aperture, a large one. An aperture so large that it fuzzes out, or "ghosts", when you mount the gun to your shoulder. You can still see the aperture, but the focus is on the front sight (as it should be). As your face is pressed to the stock, the ghost ring rear sight is fixed in its relation to your eye, so the only thing you actually have to "aim" is the front sight.
Currently I own a Remington 870 equipped with ghost ring sights, as well as a Winchester '94 that for years has been my "truck gun". The sighting system works well on long guns designed to do most of their work well inside 150 yards. On a lever action .30-30 they're a good choice, but personally I think the sights are busier than you need for a shotgun, unless you're going to be predominantly shooting slugs. That said, it works--I went pheasant hunting in Iowa with that 870, and had no problems hitting the birds.
Ghost ring pistol sights hit the market about twenty years or so ago. A number of different companies made them, and marketed them toward both the concealed carry and the competition shooting crowd. Whatever buzz there was about ghost ring pistols sights died out pretty quickly, and I stopped seeing them on competition guns well over a decade ago, which is why I was surprised to find out that a few companies still made them.
I carry a gun every day, and shoot pistol competitions regularly, and will use whatever works. I don't have ghost ring sights on any of my pistols, and I will tell you why.
First, it is called a ghost ring because the design was originally for long guns, when the large rear aperture was close enough to your eye to fuzz out. That is not the case when you mount that big ring on the back of a pistol. That big rear aperture is out there, busying up the sight picture and drawing your eye away from the front sight.
Proper sighting technique involves focusing on the front sight, not the rear. The design of a ghost ring sight tends to draw the eye to it, because it is bigger and closer to the eye. Yes, I know all rear sights on pistols are bigger and closer to the eye than front sights, but for some reason the ghost ring designs (maybe because they have an arch over the top?) are harder to look past/through.
This looking past/through sights is also an issue. I am not going to get into a discussion of point shooting versus aimed fire using the sights, but a lot of quick and dirty shooting involves muscle memory and looking over the top of the gun- seeing the sights, but not necessarily looking through them. The more naturally your gun points for you, the easier it is for you to hit what you're aiming at quickly. Gun design also helps here as well- the flat top of a Glock almost acts as a sight in its own right, drawing the eye down the gun toward the target. A ghost ring rear sight tends to inhibit looking over and down the sights to the target on quick shots.
If you think I'm making that last point up, that the taller top of a ghost ring rear sight tends to slow down close range "pointed rather than aimed" fire, I've observed the same thing at competitions when comparing iron-sighted pistols to those mounting red dot sights. Red dot sights on pistols are, all things being equal, quicker, because instead of lining up the front sight with the rear sight with the target, you just put the red dot on the target and go. However, when engaging full-size silhouettes at distances so close you're just basically looking over the top of the gun (4 yards and in), red-dot-sighted guns are slightly slower- because the sight body itself prevents you from looking down the length of the gun.
No two people are the same, and I'm sure there are people out there who, for whatever reason, may find they can shoot better or faster with a ghost ring sights on their pistol. Go for it. You see something you like, that you think may help you, you should buy it and try it.
That said, for the majority of people, ghost ring sights are not faster than a traditional notch rear. While that is, yes, my opinion, I can support it with some evidence- if ghost ring pistol sights were faster, or even as fast as traditional sights, the people who shoot for a living would be using them.
Right now, I know of NO professional shooters who use pistols equipped with a ghost ring rear sight. When your paycheck is dependent on winning, you use what works, or at least (when it comes to paying sponsors) what won't handicap you.