When I first saw that there was a section of BD from Jacob's POV (I figured this out like, the second I bought BD because I saw the Book 1- Bella page and realized that this was unlike Twilight, NM, or Eclipse) I freaked out. I was like, oh no, Steph was turned BD into a very, very, very long fanfic and the best series on Earth is now ruined. Not that I don't like Jacob--I do, but I just wasn't happy with the idea of switching POVs.
Then I read it. And LOVED IT!
Besides the fact, like jettabugfox said, that Bella's POV would have been very boring and unnatural, I realized that I liked Jacob even more than I ever had before. He was funny, caring, and loved Bella so much. I loved the pack, the chapter titles, his relationship with Edward and Rosalie, and just hearing the story from someone else besides Bella was fresh and exciting. And most of my friends, all Jacob-haters *cringe* converted to I-like-Jacob or Jacob-is-okay after they read his book. (Of course, some of them threw BD at the wall and refused to read it for a month after seeing that part of BD was through Jacob's POV...)
When life offers you a dream so far beyond any of your expectations, it's not reasonable to grieve when it comes to an end.