From wikipedia.com:
Well-bred GSDs have powerful jaws and strong teeth, can develop a strong sense of loyalty and obedience, and can be trained to attack and release on command. Poorly bred GSDs such as those from puppy mills can be fearful, overly aggressive, or both. GSDs (like Pit Bulls, Rottweilers and Dobermans), are often perceived as inherently dangerous, and are the target of Breed Specific Legislation in several countries. If a GSD is violent or aggressive, it is often due to the combination of poor breeding and the owner's lack of control, training and socialization. GSDs are often used as guard, seeing eye and police dogs, more specifically Search and Rescue, Narcotics dogs, bomb scenting dogs, which further contributes to the perception of being a dangerous breed. However, many GSDs function perfectly well as search dogs and family pets - roles where aggressive behavior is unsuitable.
GSDs' sense of loyalty and emotional bond with their owners is almost impossible to describe. They have a keen intuition or bond which is highly in tune with their owner/handler. Separation trauma is one reason they are now used less often in guide dog roles, since guide dogs are typically trained from puppyhood by one owner/handler prior to final placement with their employer, ie new owner. This is simply avoidable by proper socialization, continuing stimulation to all types of situations, with people, in and out of traffic and better guiding of their new handler/owner into the relationship with their new dog.
Temperament differences among lines
The different types or lines of GSD display differences not only in appearance but also in ability and temperament.
Dogs from working lines have very high energy, and have been bred to have a natural drive for protection, tracking, and obedience. They are bred primarily for consistent temperament, working drive, and intelligence. These dogs can be used as pets, but will be unhappy if not exercised daily or trained to do a job of some sort. The working dog lines are happiest when they have a job otherwise may show destructive tendencies.
German and Eastern European lines tend to be stockier, with shorter snouts and more muscular chests, and typify the working lines.
North American lines have a tendency towards a longer croup, longer back, higher wither and temperament ideal for companionship.
These dogs can make excellent pets, provided that a responsible breeder has not sacrificed consistent temperament or health in the quest for popular standards for good looks under the premise "if it looks like a German Shepherd, it must be a German Shepherd". Please refer to German Shepherd standards of American German Shepherd Lines and German German Shepherd Lines.
Sorry for the long read but its intresting,
http://en.wikipedia.org/wiki/German_Shepherd
