Re: Do/would you use a kid leash?
I have one and I've used it. We live in town and like to take walks. When toddlers first learn to walk, they don't want to ride in the stroller as much and they didn't like to hold hands either. With the harness, I could keep them closer, but they felt more like a big kid and could walk without running away. Also, my older girls (16 and 13) like to take the younger kids on walks. I have them harness the littlest ones who have a tendency to make a fast get-away, so everyone stays safe. There might not be a second chance if the harness isn't used and a toddler makes a bee-line for the street.
It's about safety and good parenting. Leashes (I prefer "harnesses") could be abused but a good parent will use them properly, as they were intended to be used.
I also work on training our toddlers to sit in the cart when we're shopping, or if they're too big for the cart, they have to hold on to the side of the cart. It doesn't take too many times of having to leave the store early, or missing out on a shopping trip because of bad behavior the time before, for kids to learn that mama means business and bratty behavior will backfire on them. :-)