Well, can't say I was as eager to see it as for New Moon, but, well, I really couldn't NOT see it, either.
So I went tonight, 2 weeks after it went out, and I must say I was IMPRESSED.
In my memory, the book was much more boring than the first two, but still appreciable compared to the fourth and last book in which I found everyone way out of character and the story downright absurd, either going too far into supernatural or not far enough.
Of the third book, to be honest, I don't remember much, because I read the 4 books one right after the other, so the stories are really just one to me. All I remember is that to me, New Moon (#2) was the best, then Twilight (#1), then Eclipse (#3) and far, far, far behind, Breaking Down (#4).
I was impressed, because I thought the story was poor so I thought I'd be bored, but I was swept away in the story, the characters, their struggles, their emotions... just like with the first two. I reckon that although the quality of the writing in the books is definitely nonexistent (don't give that to read to your kids, seriously,) the plots and dialogues are just good enough to make great films. Nothing to add or to remove, the books are movie scripts.
I'm also impressed to find myself in the Team Jake in the films, whereas I was definitely in the Team Edward in the books... and I always like to be surprised in films, so more points go to the films for that.
I was impressed, also, by the progress they've made in the makeup and in the werewolf special effects, both much more credible than in New Moon.
Let's also be honest: there's more male flesh displayed in this one than in New Moon, and that's always nice.
As for whether you should go see it or not, my answer will be just the same as for New Moon: liked the first two, you'll like the third. Didn't like the first two, I don't know why you'd bother to go see the third one but I'm 99% sure you won't enjoy it.