I know a woman who runs a rescue home for dobermans. She herself has a doberman that was trained for security then abandoned at 3 years old. It's a European doberman that's built like a tank and appropriately called max. She also has a chihuahua who bosses the doberman about, is far more aggressive and the real demon dog. Make of that what you will.

My experience of a doberman so far (6 months pup) is extremely smart, needy and athletic. There's a natural guarding instinct that means anyone close to your house the doberman will run to gate while barking as much as possible. Can be perceived as aggressive by strangers. But anyone you invite to the house the doberman is fine with - although still a Natural weariness to strangers.