This takes a more traditional approach to WRPG's and cuts out a lot of the pre-made characters in place of player created heroes. Compared to the main campaign, it's slightly better in structure with some decent tweaks to the gameplay and a neat, new setting to explore. But it loses a lot of the lame charm from the main campaign and the plot is still pretty dull. Ultimately it's still NWN2, meaning it's nothing to talk home about.
Has the best gameplay of the franchise due to its more open ended world map and a refreshing paucity of filler combat, but you might as well pretend that the story doesn't exist. The limitations of the NWN2 engine have grown very tiresome by this point. Has completely different design goals from Mask of the Betrayer, and I have trouble deciding which one is better. Probably more enjoyable for players who skip the base game and go straight to the expansions.