Dawn grew on me, especially during Season 7. Apparently, Dawn was written to be lot younger than actually portrayed and therefore had more outbursts and tantrums during Season 5. This is also evident with how Buffy and Joyce treated her in a few scenes. Her age was also a bit inconsistent in later seasons. While I wasn't crazy about Dawn, I loved what having a sister meant for Buffy and how that played into the Season 5 finale. It paid off, in my opinion.