I don't usually roll stats or hp for NPCs, because they are either:
- cannon fodder which is going to last 1 battle, best to use averages
- non-combat encounters, no need to stat at all
- NPCs important for the plot, in which case they are just what I want (no chance of rolling too few hps for example)
It's surprising to see how many DMs treat NPCs exactly like PCs... I've heard many groups use action points, gestalt classes, and other things, but I never thought that every monster (or at least "elite NPCs") had action points or gestalt combinations in those games.
Then of course, strictly speaking it's not possible to run social skills and experience in the same way for NPCs...