My 2 dobies are so much alike, but have such different personalities! Dar is almost 3 and I got her when she was 7 wks old from the breeder, and straight out of the litter. She is somewhat 'aloof' with strangers, and often that way with everybody! But she is so smart---she can learn something new in two or three attempts, and she is basically a quiet dog. Only barks if someone knocks at the door, or if something looks 'wrong' to her (she barked at the guy on the neighbor's roof who was fixing the shingles, cos people just dont belong there!)
Sasha, on the other hand, is a rescue, and is sooo loveable, she wants to snuggle and would crawl inside your mouth if possible! She just can't get close enough! But she is hard-headed, and it takes a very long time to change certain undesireable behaviors. She was almost a year old before she was totally housebroken, she still will get into the trash can unless it is emptied continuously, and she loves to bark at everything under the sun that moves! I tell people that she is a work in progress. I took her to a basic obedience class, and she tried to snap at a Pom (well, she was sort of provoked by the little snot, but that's beside the point) You dont try to eat your classmates! The next class after that episode, the instructor said, "would you mind moving Sasha to the END of the line?" I sure hope she gets a little better manners soon.