I saw Steranko at SDCC in 2006 at the Vanguard booth. They had an end booth as I recall, and it extended into the first booth on either side, so it was a big space. Steranko stood in the middle of it and pretty much didn't make contact unless an item was purchased. I took him to be stand-offish, but this seems to be the exception rather than the rule.
My first Tony Moore meting wasn't stellar, he just didn't seem interested in being there. I met him again this year in KC and we struck up a conversation about Fear Agent, going on about the EC comics that inspired it. Complete 180 from the first time.
Meeting Jim Lee was a downer, but again, by all accounts, I just walked up at a bad moment. He never looked up, just scribbled his name and kept going. His handlers are the only ones that spoke, and all they had to say was "hurry up."
I don't get that about the assistants at the show. If you spend all that time lining up to give your money, they can wait a few moments while you prepare exchange when you get there. I don't risk my cash being exposed or comics/art being damaged while I am in line. If they don't like how I am giving away my money at the front of the line, too bad for them, not too bad for me.