As I observe our agility classes, I also find that Border Collies are excellent at agility. I agree that they are very, very active dogs the rest of the time, too. They need a lot of exercise and work to keep them happy! There are a lot of Goldens in the classes, too. My GSD is a slow-poke at agility. She'd rather go look for me in the crowd and then go back and do the course!
Sue