The Path books had a lot of stuff I would never use. But there's some stuff in there that is pretty neat. I am not too hip on the styles or the variant core classes, but many of the PrCs are good (though MANY mechanics need updated... I straight out decided not to use daughter of storms with one NPC and used stormcaster from stormwrack instead... 3.5 call lightning gutted the class abilities for that one), and if you dig the idea of legendary classes, those are way cool.
The organizations are neat, but I wouldn't use the mechanics for them.
The Lore Books are some of my favorite monster books (esp. necromantic lore), but I neglected to mention them because I got them long ago.
The school books suffer from 3.5 conversion as well, but I think School of Illusion really helps shore up the illusion school spells; as is, I think illusion does not get the attention or utility it deserves. The PrCs are neat in both school books, but again I wouldn't touch the base classes.