I use them so that I do not have to bend my neck to read a book or newspaper.  It takes a while to get used to using them but they do work quite well.  Worn over reading glasses is not comfortable but acceptable.  The resulting image is smaller than using spectacles directly.  If your eyes are different from each other, hence needing reading glasees, the image in each eye is not as co-ordinated as it is without them.  Overall they do what I want them for, and the advantages outweigh the disadvantages.