I just bought the pistol grip autoloader from CDNN ($699.99 - $499.99 for standard stock). I have not shot it yet.
Keep in mind that while HK will service the shotgun, HK is not importing Fabarm any longer. Sigarms is the new importer and it is not importing the law enforcement guns (at least that is what I was told when I called).
This is my first shotgun. I wanted a semi-auto, a pistol grip stock with a shorter length of pull, and a reversible safety because I am left-handed. The Fabarm had it all at a decent price.