Ben,
Charlie has learned to be calm around other people. He's actually quite friendly now, but the first time friends came over after I got him, he lost it!! He didn't hiss, but he meowed loudly and ran into my room and under the bed as if he had a monster at his heels! When I tried to bring him out, he jumped out of my arms wildly and ran back in the room. I thought he was terribly anti-social, but it turned out ok. He is now almost 1 year old now, but it took several visits from friends for him to be totally relaxed. Maybe Zezu will still grow out of it.