I think they're tacky, but for full disclosure, I think infants look absolutely ridiculous in headbands.
Add me to this camp. I think headbands look really, exceedingly weird on newborns. I understand the practical reason, though. Newborns are androgynous, and sometimes you just don't have anything pink left clean for her to wear. So, you want to make it clear that she's a she. I get it, I just think they look weird.