Cats are more fun in pairs. They have company when you're at work, as well.
I am in full agreement.
My current cat does NOT like other cats. Or dogs. Or humans. She basically only likes me. I have a roommate that my cat has lived with for the last 3 years, and she still won't go anywhere near him unless I am also in the room.
I would love to get another cat to keep her company when I'm gone, but I don't think she would want anything to do with it.