Based on the Border collie we had when I was a kid, I used to think I never wanted one. She was out of control, chewed on everything, herded everything, and we spent all winter chasing her down when she ran off. As it turns out, I LOVE the breed. Our girl was just undersocialized (we got her at 3 months old and she had been tied to a dog house for a month), underexercised (my Mom wanted a lap dog and my Aunt dumped this one on us), and totally untrained.
But I love training dogs, love doing agility, and love taking walks and hikes. I decided a couple years ago that BCs are really the breed I'd like to own someday.