I love the storyline of Dawn, the purpose of Dawn, why Dawn exists... but Michelle Trachtenberg as Dawn bugged me to holy hell in Season 5. Her face on the screen would bug me occasionally - it was hard for me to watch her scenes sometimes. Even more so the second time I watched the series. But, thankfully, she bugged me a lot less in S:6, and even less than that in S:7. I like that she grew up with the seasons. Yay for the fantasticalness of the Buffy writers! 😉
I liked her most in S:7 and having just finished that season again for the second time the other night I think a lot of that has to do with her whining ratio going from like, 90/10 to about, eh, 20/80. I liked that she got into Demonology and became an asset, a mini-scooby, to be precise.
So really, kudos to Michelle T. for being sooo good at being annoying, and being sooo good at 'growing up'.