mamazee, I love answering simple questions and sharing my terribly important opinion:-)
I have no problem with a leash (I think they are also called harnesses) )because it is so much better than a stroller and still contains the child if used correctly. My son is ripe for a harness being almost 2, and I don't think I have to explain the multiple locations where a stroller is inconvenient and deprives a child of the exercise and holding hands and expecting a child to cooperate is just unrealistic.
I would probably not use a harness through a busy street with moving cars or other hazards because of the risk of it breaking.
Its funny that you mention it breaking.....after a couple of months of using our monkey backpack harness we went to a street fair/concert. My then 20 month old saw something very exciting and bolted. The leash began to unravel as he ran. Thankfully it was just a crowd of people (no cars) and I laughed so hard watching my husband chase him down. That was the end of our leash experience, although he still loves to wear the backpack at 4 yrs old. I think we have to give parents credit that they know their children better than we do and I think most people use it for safety more than convenience.