I have it and frankly it's awkward to use for anything but the front, or all the area that you can see without the use of a second mirror. It does help you use less of it, but it's easier to just use leave the normal cap on it and sprinkle as normal. Its biggest pro is for spot treating areas. Outside of that, it's impossible to operate while holding up a second mirror to sufficiently cover the vertex.
I'd recommend people pass on this.