Although I have heard it as well, but when I met her in NYC she was nice, err at least to me. Signed everything I had and took 2 photos with me. Then I ran into her again in NYC on the street, didnt have anything for her to sign since I wasnt expecting to see her, but she stopped for every fan that came up to her on the street.
As for Michael Biehn, I met him awhile back right after Planet Terror came out. He wasnt a jerk per se, but he did not want to be there and his prices were crazy even prices to get a photo with him. A year later I met him again at another con and it was the complete opposite, hell he even smiled in the pic the second time around.
Its really hit or miss, any given day someone can have a bad day....granted if they are getting paid to be there then they really should suck it up and realize its the fans that keep them in business.