At the risk of being thumbed-down infinitely, I'd like to go on record saying I absolutely loved Stormrage.
/ducks in cover
Why? Lines like "I don't want your damned candle!" :D I loved the little details. As an alchemist, the creative use of Dreamless Sleep Potions made me laugh. Likewise, the description of hearthstones as a rare artefact seemed to be a joke shared with the reader. There was a lot of acknowledgement of the players within the novel (the group of adventurers who free Naralex from the Wailing Caverns, for example) and many of the most powerful heroes were written among the first to fall prey to the Emerald Dream, but perhaps people were miffed about their personal favourites missing out on the action?
People argue that Knaak's characterization is weak. While it's true that he focuses on the hero in action as opposed to the hero in everyday life (like Golden) I don't know that characterization is so much weak as contrary to the reader's preference. I've heard numerous female readers complain about how Tyrande is portrayed, ironically because she's not powerful enough. (How dare she learn from Azshara's pride? Where's the self-assured leader from Warcraft III who thoughtlessly slaughters Maiev's Wardens to free Illidan, then gets herself captured by Illidan, overwhelmed by the Scourge, and then saved by Illidan in The Frozen Throne?)
As for the characters being too powerful, many of the heroes of Azeroth fall prey to the Emerald Nightmare before the novel even begins. Ultimately the heroes triumph, but then we knew they would, didn't we? The game must go on...