I was catching a lot of flak about this call from the grizzled vet'rans in my group in Saskatchewan last year.
Once we got out to the potholes, this thing worked so well that they left me alone and actually asked for more. They were really surprised.
You can operate it one-handed and out of sight from above. It just takes some good wrist action -- which, of course, opens you up to other smart remarks, but you can't have everything...
It produces the difficult-to-master feeding call very effectively, even for a novice. If you have ever suffered through a hunting buddy doing the feed call badly -- and, most people do it badly -- this call if for you.