Michael Varian wrote:
Is aikido useful in self-defense situations? Why or why not? What are good self-defense arts? What aspects of a martial art make it useful or not for self-defense? What are the factors that decrease the time required to be functional from a practical standpoint? Is self-defense even important?
IMHO, yes Aikido is still a martial art, therefore important and useful in a self-defense situation.
It takes longer because you not only have to learn a different way to move, but also a different way to think. The change and unity of body and mind is not a simple task.
To decrease time, go slower initially and learn the technical tactics and the strategic principles and concepts.