The adept class

[Jhamin]

I find that Adept levels work pretty well for "hedge Magicians", folks that you want to give some potent abilites to, but don't want to give the full powers of a PC spellcaster.
In my game, I have orc tribes led by Barbarians and Priets of Gruumsh. But even the orcs don't like to annoy the old hag outside the villiage with her strange powers.

For that matter, most all of the NPC classes serve their purposes. I kind of like that a brawny farm hand (lvl 3 commoner) cannot be dismissed by a low level fighter in a bar brawl. Sure, he isn't going to win, but at least he isn't a 2 hp nobody.
And when the town guard (War 3) comes in, they aren't as good as the party fighters, but they aren't idiots either.

 

[Zenodotus of Ephesus]

Adepts work quite well as low-level spellcasting generalists and as the DM I can distinguish them as divine or as arcane by my choice of spells. The spell list in the books is only a guideline and I don't feel tied to it. If I need something more specific, I can use the Cleric of the Wizard PC classes. If I need something even more specific, I can use a PC class with a Prc on top.

 

[Li Shenron]

Am I the only one "bothered" by the adept NPC class? It has both divine and arcane spells, from multiple class lists. I mean, for a class that supposedly comes from little or no official training (the hedge wizard concept), it has somehow managed to draw magic from several directions. A wizard with all the training in the world can't cast cure light wounds. A temple-trained cleric can't cast lightning bolt. Yet the uneducated po-dunk mystic over there can do both. Even the sorcerer, for whom magic supposedly comes "naturally" can't cast some of the spells that a mud-faced adept can cast.

I've never used an adept in my campaigns.

I tend to outright ignore all NPCs classes. If I want "weak" opponents for the PCs, I just let them face lower-level NPCs. Otherwise, for really non-important NPCs I don't even really stat them out but just give them a bunch of Hp and the score in what they are supposed to do (usually the attack modifier or a skill modifier).

I have used NPC classes only when they were already used for NPCs in published adventures, in which case I didn't bother to "rewrite" those characters.

After all, I think that NPCs classes are quite unnecessary after level 1st. The Adept seemed to me unneeded even at level 1st, where it is almost the same as a Cleric.