I absolutely adore the character of Dawn. I have never found her to be too annoying or whiney.
I mean ALL of the characters in season 6 had major flaws, were annoying to various degrees, and all were shown to be whiney about their problems. All of the characters whined about their lives, were responsible for their massive problematic situations, and were passive aggressive about getting their acts together until the later episodes of season 6.
Plus we all know that Buffy for the majority of season 6 did not try her best with Dawn or anything else in her life. She was just going through the motions with everything. Buffy failed to realize or see that Dawn and everyone else in her life was in pain and had been hurting from the events of season 5 and season 6. This is where Buffy failed Dawn and herself last season. The older characters all made some huge, dangerous, and stupid mistakes in season 6. They all have had way more experience and knowledge from previous seasons than Dawn possesses. I will always cut Dawn major slack because of this fact.
So I don't see why Dawn gets complained about more than the other characters because the fact is that the other characters last season made more major mistakes in season 6 than Dawn ever did in her short life. I saw much improvement in Dawn in the latter episodes of season 6.
I think Dawn is a cool chick who has a good sense of humor and is very smart/perceptive. Plus I think Michelle T. is a babe who is a very good actress. Dawn kicked major ass in the finale. She has proven her worth to Buffy. Michelle, Joss, etc. all say that Dawn will grow up, become more mature, have a purpose, help with Scooby matters, and that Dawn/Buffy will connect better as sisters.
So I can't wait to see the new improved Dawn in season 7. I think Dawn will get some good development, be connected to the main stories, and be an important contributor to next season. I have faith in Dawn!
Dawn is my fave character on BTVS and Michelle is my fave actress on the show. 😀