I saw a guy lose some teeth shooting a pistol-grip shotgun from line of sight. Couldn't get there in time to stop him. It can be done, but it's very tricky and technique intensive.
There are a handful of people who can shoot the things very well -- the great Mongomery County, Ohio Sheriff's Department instructor Terry Campbell comes to mind -- and one of my clients used one to kill a guy a few feet away who was coming up on him and his partner with a loaded .30-30. An East Coast business owner used one to win a shootout with multiple armed robbers a few years ago.
That said, I don't recommend them. Any place you can store a PGO (pistol grip only) shotgun, you can store one with a folding stock...and if there's time to go for a long gun, there's usually time to unfold the stock.
Just one guy's opinion,