Haha, major error in the title there!
Anyway, I've got it and it improves in a lot of ways on the OC, while sacrificing in some parts to most importantly MotB. Where MotB was strongly character and story driven, using personal choices for consequences, SoZ is gameplay focused, providing (for the first time) challenging combat in the NWN2 engine, usage of tactics and above all a major revival of the usage of skills. There's hardly any skill which is unused or useless in this game.
That said, what makes SoZ great is the old-school vibe. It's a tactics game, using towns as bases for resupply and rest. You go to the overland map, and based on skills see certain encounters and can avoid them etc. From here you can go to other places of interest, if you have the skills to find them. An early example: right at the beginning you're supposed to fight some guys but you have no gear. You can use various skills to fashion improvised weapons or even find slightly better stuff using search/spot. This is handled through a dialogue screen, in which you can select the party member doing the 'talking'. Thus you can spread skills across your party and select whatever is necessary.
So in conclusion, if you like statbased adventuring without so much the fleshed out npc's or grand story, go with SoZ. Otherwise, MotB is still king. I would compare them this way: MotB = PS:T 2, SoZ = IWD 3