Oh, I didn't mind that they weren't front and center, but Narcissa had been wavering since the beginning of "Half Blood Prince", so it was fitting that it was she who lied to Voldemort about Harry's being dead, at the end, when he whispered to her that Draco was still alive.
She must have been a hell of an Occlumens, like Snape, if you think about it. Within a second of speaking with the very much alive HP, she turns around and lies to LV. It's been stressed a number of times how LV could almost always detect a lie--"The Dark Lord always knows!"
At a panel discussion at this past year's Lunacon (in Rye, NY) with a couple of Potter fanatics, I brought up Narcissa and made a comparison to that freaky-looking mother on "24" a couple of seasons ago who was ready to betray her cause for the sake of her son. They nodded agreement, and then murmured something about, "And look what happened to the kid!"
Narcissa should've been thanked (or at least acknowledged) along the way. Without her, the war would've been lost right there. (Granted the book was getting a little long by that point, so maybe not...)