i fucking hate writing ...
I agree with this, although I would point out that it is possible to "bake" mishandling right into the published module. The wizard from N1 is an example of this; a lot of ink is spent on dealing with the fact that you have added a much higher level wizard to the party just so you could have a tougher boss monster.The real caveat to NPCs is mishandling. Usually goes away with practice.
Yeah, exactly. A good NPC is more of an interactive (some would say the interactive) tool, rather than being an intrusive element.Also, I wouldn't call it an escort mission if you get to choose whether to bring the NPC. You may want to bring a fragile NPC who unerringly detects traps, for instance.