Couldn't make it through all the posts, but here's my 2 cents:
I used to think they were horrid, and then I had to fly alone with my 6 mo old and 2 year old. The thought of trying to run after a 2 year old in a crowded airport while dragging luggage and wearing my baby was too scary. I bought and used a harness, and any concerns about what others thought didn't really matter.
WAHM (natural childbirth instructor) mommy of three boys, Kindergartner, Preschooler and newborn.