I just finished this morning and, JMHO, I thought this book was only so-so. I feel like what carried it was the characters and the image of them we already had in our heads, they are brilliant characters. But the plot lumbered to me, and I didn't see a lot of development among the supporting characters. By the end characters like Tonks and Lupin, who seemed like they could have been really interesting in this book, were just cannon fodder. I know it was a book about a war, and many people die in war, but the deaths seemed to hurried and sort of haphazard to me for a series that painstakingly developed its characters up to that point. Just my 2 cents. I'm waiting for the sequel series about the adventures of Teddy - after all, he's the new orphan of the group!
BTW, twinkletink, number 3 was by far my favorite too!