The one problem we're having is that occasionally if you go to pet Ben, he thinks it's an invitation to wrestle and tries to disembowel your hand. Not at all uncommon behavior in cats, god knows, but rather unsettling, since he's very strong and we haven't yet figured out his body language enough to know when he's in that kind of mood. (Athena telegraphs it very obviously, bless her dim little heart, mostly by rolling on her shoulders and biting the floor.) However, it definitely seems to be misplaced play behavior, rather than aggression--humans always have to intiate the contact, and in cases where he'd normally display actual aggression, (i.e. with Athena) he's an absolute pacifist. And he doesn't make any I-want-to-kill-you sounds--he just seems to think that it's a free-for-all, and doesn't really understand why we yelp and recoil.
He wasn't doing this when we had him in the spare room, so I think the increase in frequency is largely due to several days of living with the constant stress of Athena wanting him dead. (Lord knows, that'd probably get me keyed up and wanting to blow off steam too.) I'll go back to giving him a few hours alone in the spare room a day and see if that calms him a little--possibly he just needs a break where he knows he can nap without keeping one eye open!
I suspect this is one behavioral problem that'll work itself out once we all learn to read each other a bit better. We did figure out that he hates to be picked up if he's laying down, but if he's standing up, you can pick him up just fine--he's not keen on being carried for long distances, but he doesn't flail or claw. He just doesn't like being picked up when he's laying down, for whatever reason.
Eh, cats. What can you do?