This is a great thread, thanks everyone for your imput and all the information!
When DS was little I was really against these leashes, but my child never ran off either. A friend of our had a boy who would take off - fast. The leash was, perhaps literally, a lifesaver for this family, it was the only way you could handle him in a crowded place.
I am considering getting one of these for our upcoming trip. I don't personally mind chasing after my youngest child, but she will be spending alot of time with my mother at WDW, mom has arthritis in her back, it hurts her back to stoop to hold DD's hand, and if DD gets away mom can't move very fast if she needs to chase her.
And sure there are people that look down on leashes for children - I used to be one of them! While I still don't think they should be used every day, they are great when you realy need them, and WDW is one of those places where they are useful for some families.