I used a harness for my youngest until she was 3.5 years old. She loved the freedom it gave her, I loved that I didn't have to have my eyes glued on her every second she was outside. It was especially useful when we went to local carnivals, into the city, etc. where there are crowds of people to get lost in or heavy traffic. I highly recommend the harnesses!
Yeah, I heard comments about treating her like a dog. My response was "Most people treat their dogs better than they do their kids." I knew my darling daughter was safe, that she was happy with the arrangement. That's all that mattered to me and my DH.