I'm playing as a Necromancer. However, other than not being able to cast Divination spells this seems to have made no difference in terms of spell-casting. The extra spell specialists used to get from BG is gone. Am I right or am I right?

Being a specialist does allow you to cast an additional spell at each level, just like in BG. So it is definitely worth your while to specialize.

Yeah, there is the additional spell per lvl, and if I remember correctly, you get slightly better chances to save against your specialized type of spells, and the enemy gets a slightly lower chance. Pretty sure that is the way it works in NWN.