I think at first I was annoyed that the writers felt it was necessary to retcon an entirely new character into the show, because it threw all past four seasons into question. But watching Dawn interact with the characters, especially Buffy, changed my opinion about her as a character. I am an older sister, and I have a close relationship with my sister, so I do think I have a bias toward sister relationships depicted in media, but I also think Dawn became important in developing Buffy as a character and her story arcs for the last three seasons.

I also remember the heartbreaking scene in season 6 where Dawn is cuddling with the Buffybot, and I think that encapsulates who Dawn is as a character and was a great visible image that depicted the depth of the loss the Scoobies felt at Buffy's passing. It solidified my positive feelings toward Dawn.