The backpack ones, definitely.
People who scoff just don't understand that you're doing it because you LOVE your child and you KNOW your child.
My mom used harnesses with me and my brother, and we had a grand time wherever we went. Now, was I able to use one with DS? No. He liked to mess around with it, which resulted it in looking like I was hauling him around against his will. He was leaning into it, having fun, or running to the end to see what that would feel like...it was embarrassing when people would see the end result (me trying to get him "back" instead of what he had just done gleefully), and it was painful for me, so we had to figure out different ways of reigning him in. Oh well!