Psion said:
I don't hate it, but I don't use it.
It seems a bit specialized to me for a core class. I could see it as a core class in a campaign where there are a lot of spellcasters, like Brust's Dragaera. In my campaign, I try to play off mages as a bit more unique, so I wouldn't see a broad body of thiefs dedicated specifically to preying on magic as credible. It would be very much a specialty thing, like I normally think is appropraite for a PrC.
Good point. I think the spell thief is a very interesting class design and one that WotC does not do very often. They have taken something that could be done with a core class + a prestige class and stretched it out over a full 20 levels, resulting in a base class.
This is something that a lot of other companies do with their base classes, and I usually don't like it. In the spellthief's case, I think it works, but I would really not suggest it as a general method to design a class.
What I like about the spellthief is that they have a very unusual set of abilities, and they get their core ability at level 1. You could do a prestige class with much the same results, but you would likely have to smash together all of the abilities quite a bit more, which I don't think I would like nearly as much.
With all of that said, the spell thief fails the "is this class a broad archetype" test badly. It is so specialized that it really does fit the definition of a prestige class much better.
You're also right in saying that it would only really work in a certain kind of campaign. A game where there spells and spellcasters are rare would make the class fairly useless, as would a game with a lot of psionics.
Still, from playing one a bit, it seems to be one of those "do anything and everything, just not particularly well" classes, like the bard. All I can ultimately say is that I'm enjoying playing one, and it doesn't seem overpowered.
--Steve