What people notice when we do a demo is how much fun we have. People are smiling and laughing as they get thrashed. Folks aren't used to seeing that joyful side of training when they think of martial arts.
Further I think that adequate coverage of the origins of Aikido, who the founder is, how it evolved etc. are important points to give people a framework of what they're looking at. Also the intent of Aikido: one intructor at our dojo is jiujitsu guy also: he likes to point out the differences in the JJ form of a technique and the Aikido implementation.
side note: we did a demo a couple of weeks ago for a local Japanese Society. A bunch of white guys demonstrating a piece of Japanese culture for a group of Japanese people. Funny.