Well.
When we first purchased Happy from a farm, supposedly he came from some Amish folks some town a little ways away. My parents told me that his papers(which I never seen) read "Australian Cattle Dog", which, is absolutely wrong. Eventually I found a site with Australian Shepherd information, and immediately made a connection.
After some thought however, I decided(at the intellectual age of fifteen) that because of his physical disposition, Happy couldn't possibly be a complete Australian Shepherd. I thought we saw and felt some Border Collie, so I would add that - And he became a Border Collie-Australian Shepherd mix.
Now days when I look at him, though, I feel as though I'm not sure if I can really say that. I know he is partially, if not all, Australian Shepherd just by physical attributes and behavior alone. But I wonder now if he was just poorly bred, or perhaps bred from working-dog stock, and I really don't think I can safely say exactly what he is.
So, Aussie mix works well most of the time