I own them, the original three Witchfire, and to me 3.5 was a horrible mix. I loved the setting, though, still do to be honest. I'll have to wait a bit to save up the pennies, but I plan on getting the core book soon.
From what I understand, it's a stripped down version of their Mini's rules, with more fluff attached, to give background. Not to mention a balancing of Warcasters, making them playable without overpowering non-Warcaster players. Also, again, from what I heard, it uses a similar system to the Warhammer Fantasy Roleplaying Game's Career system, in which you start with one or two and take things from each, and over your adventuring career (no pun intended...) can pick up more.
All in all, sounds cool, and it's on my Too Buy Now list. I just CAN'T buy now.