I started using the GU Box Launcher last year when a guy from our club was getting ready fo the Master National. It works great for walk ups. Its easy to hide and gives a large enough throw for the closer range. For work under 50 yards they are fine but if your thinking longer then go with a winger.
As for the distance- We used mallards but really Dokkens work better. I would guess they throw a mallard about 15' high.
I now carry it on the trailer all the time.