Well for me, I dislike Bella because she is whiny and annoying. I hate how she always looking down on herself. Every three pages she is all "Edward is so beautiful, and I so am not worthy." It really makes me want to punch her. She doesn't accept presents hurting peoples feelings in the process, and what really kills me is that Edward thinks of her as a perfect selfless angel when in fact she is not. I mean, she basically forces him to change her into a vampire so she can be with him. How selfish is that!? I just want to hit something just thinking about the annoyingness that is Isabella Marie Swan!!! But I must say the Bella that is in DaydreamBeliever's fanfiction Changing the Future I have hardly any problems with. Speaking of, there is a new chapter up and I must go read it.
And concerning the second part of your question, I personally don't have that much of a problem with Breaking Dawn other than wishing there was some sort of battle and I find the imprinting on a half vampire child completly creepy, I mean, how would that support the theory that wolves imprint to find the one that will give them the best ability to reproduce more wolves, and the fact that Jacob loved her mom.
"Jacob, have you loved anyone else before?"
"Well 'Nessie,' there was this one time I was in love with your mother, but that was before you were born, so it's all good."
*shivers*
But again, that is just my reasonings toward both topics.