I've owned one and hunted over several others all were decent bird dogs, that being said for bird hunting I prefered English setters.
Back to the German Shorthair I owned, he was an extremly ill tempered dog.
I could not hunt him with another dog, he would kill them and made short work of it I might add.
He would retrieve to anyone, however whomever was hunting with me that day better not step in my yard at home as he would go after them with extreme aggression wanting to bite them.
I always had any hunting partners wait in the truck when we got back to my place until I had him secured in his kennel.
He bit me once, paid dearly for that mistake and never made it again.
If I was not home and my wife would go out to feed him she never went in the kennel she would slide his food pan under the kennel door.
I believe the above ill tempered behavior is not typical of the breed as I've hunted over several that was nothing like the one I owned.