In The Fires of Heaven, the narrative is largely split between Rand as he returns from the Aiel Waste and Nynaeve's struggles against Moghedien. 
 I see that a lot of people didn't like the focus on Nynaeve. She's always been rather critical and negative, but she's been something of a side character, so that she is only experienced through an intermediary. Here, though, we get a whole bunch of pure, unfiltered Nynaeve. That means near constant criticisms of men's wool-headedness, abject hatred of Juilin's hat, and her cattiness with Elayne. 
 Personally, though, I actually appreciated it. Because while Nynaeve is certainly very negative, her character is also growing a great deal through this book. After her victory against Moghedien in the last book, she now has to deal with the fact that a member of the Forsaken has taken notice of her and has a rather big grudge. She tries to deal with her fear and guilt by transforming herself into a meek woman, only to be brought back up by her friends and to realize that she cannot be meek if she is going to do her part to save the world. 
 Mat Cauthon continues his own transformation. I really didn't like him when we first met him, but he is turning into one of my favourite characters. His constant cycle of trying to escape from his destiny only to be pulled back against his will is rather hilarious. 
 The pacing is slow, and I agree with the complaint that it tends to be very slow through most of the book only to suddenly speed up for the climax, making the book feel rather uneven. That said, though, I appreciate how much depth the characters have, and how much they are changed and impacted by their experiences.