I bought the Family Grain Mill with KitchenAid adapter---different mill than the one you're talking about, but same concept.
I had to run the grain/flour through no fewer than 4 times in order to get a passable flour. It was still too coarse to really make a good bread, though. It took me well over an hour of running time to mill just one pound of grain to this texture. I had to sit and babysit the thing to keep the grain running through. Add to it the fact that you need to let the motor of your mixer rest every so often in order to keep from burning it out, and it just wasn't working for us. We are just a family of 4 (two adults, 4 year old & 1 year old kids) and there was NO WAY this mill was going to keep up with our needs.
I had purchased this one because I had read reviews stating that it was better than the KitchenAid brand one.
I sold it and bought a Nutrimill off of Ebay, and am extremely pleased..