I have installed these sights on several different handguns for clients. Generally, the clients are older people with the nearsighted problems that come with old age. About 1/2 the clients liked them and will use nothing else. The other half did not like them as they effectively covered up the target and did not allow for shooting optimum groups.
I personally do not either need nor like them. But they are a solution for some. IM if any questions. Charles the Gunsmith.