An uninspired plot that seemed to be tacked on to the Neverwinter Night's game universe.
Anyone who has been playing Neverwinter Nights since it's inception has gone through the highs and lows of a well-crafted game experience. We saved the Sword Coast from the wailing disease, cracked the secrets of the flying Nether city of Undrentide, and journeyed to the depths of the Underdark. After
getting everything out of these stories that we could, we started writing our own - persistent worlds popped and many aspiring and well-established DMs wrote their own stories to take part in.
After getting past the initial technical difficulties of the launch of NWN2 we dove head first into the fantastic stories behind the Shadow King and we were driven through Rashemen by our new-found hunger for souls. All of these chapters in the history of the Forgotten Realms told compelling stories; they all significantly altered the world they took place in; and they all introduced new characters, classes, or game technology.
The problem with the SoZ is that even though it introduces some potentially great concepts - such as the explorable over-world map, a trade system, new uses for Spot, Listen, Search, Survival and hide, new classes, and a new party-conversation system - all of it was buried under a bland, uninspired plot experience. Many of the new technologies are also buried under their uselessness in respect to the SoZ campaign. While trading seems interesting at first, after you have a caravan or two under your belt, money is no longer a concern. Side quests, for the most part, have no relation to the plot. And the difficulty of the random encounters don't scale with your party.
Lack of difficulty scaling is potentially a major problem, because there is no upper limit to the character levels you use to form your initial party. There is nothing really stopping you from bringing in your level 30 hero from Mask of the Betrayer with your practically infinite wealth and unbeatable equipment and just breezing through the loosely-strung together story. Even if you start with fresh level 1 adventurers, the campaign will be hard-pressed to last more than 10 hours. The actual progression is very short, being about 25% of the game, with the rest filled up with random side quests and random encounters.
Unless you are a developer of persistent worlds, an aspiring dungeon master who wants access to the new features of SoZ, or a die-hard Forgotten Realms fan, I would be hard pressed to recommend this game to the casual gamer.