Throughout Twilight, New Moon, and Eclipse, we've come to know Bella Swan as our narrator. We see the world through her eyes and experience her emotions. In Breaking Dawn, Meyer chose to let Bella narrate the first part of the book, and then switched to the narrative voice of Jacob, only to return to Bella as the narrator in the last part of the book. Why?
Here's how Meyer explains her choice:
In the first rough draft, it was Bella throughout the entire story. There's this section of the story where Bella's pretty much stuck on a couch and is not part of anything that's going on, and she's just hearing about it from the outside, and it's boring! [...] So when I went back to do this, I realized that where the action was, was something we can only get through the first-person perspective of Jacob. And once I made that decision, I was really glad I had, because that was the most fun section to write out of the whole story. (source)
So the main reason for the point of view shift was not to bore us. Very considerate. Did it work? Does Jacob's perspective add to the story? Or does it take away from us being inside Bella's skin, feeling her pain and her fear for her baby and for her own life? At any rate, Jacob's narration makes us insiders when Jacob imprints on Renesmee, even before Bella learns the news in the last section of the book, which arguably builds suspense about how she'll react.
Also, Jacob's change of heart from wanting to kill Renesmee to devoting his life to her would probably never have been as powerful if narrated by Bella.
Other reasons to consider are that not knowing Bella's perspective could makes us feel more helpless to watch her because we care about her. Or did Meyer think it was too painful for us to experience it with Bella? Or did we need to feel, like Jacob, hostile toward that "monster" that was going to kill "our" Bella, only to fall in love with her, like Jacob?
Meyer's other reason to switch to Jacob is, as she says, the simple fact that she loved writing Jacob. But does she, as an adult woman, do a good job of portraying a teenage werewolf boy? How successful was she at taking on this new personality? Did she make Jacob more real for you?