Tried the +2 grip extensions last Fri.
They installed easily, but getting them off is almost impossible without damaging the grip extension. The instructions say to gently squeeze the magazine (yeah, right, ever try that with a Glock magazine?). I can easily remove my standard base pads by shoving in a pin punch to push the floorplate from the bottom to against the front wall of the magazine, and, while leaving the pin punch between the floorplate and front wall, using the pin punch to lever the base plate off. So, unlike my magazines with standard floorplates that get disassembled and cleaned regularly, these magazines can't be cleaned.
They do provide a better grip on the gun, but it isn't quite as good as a gun with a full 3-finger grip. I am totally used to the abbreviated grip and do just fine with it. My wife prefers the 3-finger grip, but complained about the textured front surface of the grip extension.
Two extra rounds in the magazine is of course nice.
The verdict: they won't be used for my carry magazines, but will be kept on some practice magazines to help my wife shoot the gun.