I found two main effects. Right-clicking on an NPC should open a little window which gives you the NPC's name and occupation – e.g. Tabitha, Wind Master. (Except for the peasants in the Temple on the island in Blackshire, whose name escapes me just at the moment.) On the faster computers, however, not every NPC is assigned a name and occupation; a significant number of them just flag up as "Peasant".
The other difference I found is that on the old slow computers, searching the pews in the chapels of the two buildings housing the Silver Helms will give you a decent spell-book in one case and (I think) a good staff with a decent enchantment in the other. On the new fast computers, these are not found.
I strongly suspect that there will be other differences as well, but I've not explored in detail, and it's possible that the differences may very from one computer to another.