Most of these- if not all- suck. Think about it: You are trying to adapt the internal iphone lens, which is a moderate wide angle, to do something else by sticking some other lens in front of it, and in order to have any kind of optical performance att att (not even considering the kind of design compromises the adaptation requires), you've got to line it up within optical tolerances, meaning microns (a micron is a thousandth of an inch). Like to keep a case on your phone to protect it against drops and knocks? You'll need to remove it every time you put the lens on. I haven't seen results from the specific one you saw, but the results I have seen from add-on lenses have left me very underwhelmed. Think of them as the optical equivalent of those crappy battery-powered bluetooth speakers you see everywhere- they're satisfactory enough if you're not too critical, or if you've had a few.
