Endings in general are worth more than their weight in paper, because they either give the story's journey a destination, or they make the entire story pointless.

Hmm. I guess I look for different things in books than you do. I like the journey of the story. I really do not care too much about where the journey ends or starts. I like the middle. If the middle is crap in a book I will never, ever read it again. I can endure a bad beginning or a mediocre ending, but if the middle is a desert I have a hard time liking the book. If 70% "blah" leads into 30% "wow", why did I bother with the first 70%? Give me a summary of the 70% and let me read the good parts.

I suppose some of this sentiment comes from the fact that there is no good reason for any part of any book to be blah. 70% bad and 30% good is strictly worse than 70% good. There are books that exist where the entire thing is worth reading and I only have so much reading time.

Another guess at the source of this sentiment is that I actually enjoy the writing. I like good writing as much as I like a good story. I enjoy books that are about nothing in particular and have no great story to tell if they are written well. 70% bad writing is not worth 30% good story.

Of course, as I mentioned, I am not talking directly about Twilight since I have not read more than a few sentences.

The last book (slightly more than 25%; it's the longest of the four), in this case, provides a well-worth-the-wait payoff for the slow pacing of the first three.

I am not really talking about pace. I like slow pace if it fits.