I don't care for strollers for walking age kids either. There is a time and place for them but kids really shouldn't be in them more than needed. I think we need to get kids used to being active really young as it also doesn't get any easier when they are older. Our just turned 3yr old can bike (balance bike, no peddles) 4km roundtrip to the park on her own because she's been working up to it since she could first walk. She can walk (and snowshoe) equally long distances (2+ hrs) when we provide the time she needs.
It all depends on whether we use these instruments (strollers and leashes) as a teaching tool or as a 'make life easier for adult' tool. Again, we need to be thinking ahead as to what we want and expect the child to be capable of in the coming years and work towards that now.
While I think the look of the harness elicits negative reactions I suppose it would in fact be better than a 3 yr old strapped in a stroller because at least they are moving!