Stormprince said:
And for the record, our Magic System is completely OGC... except for the descriptions of magic items, and the names of certain creatures (pecwae, bahk, etc). We've kind of had a curiosity going to see if anyone else picks up our magic system through OGC, just for giggles and grins 
Christopher
I know I would if I was in the business. It would be nice to see a demonology supplement to the system. Maybe I'll make a netbook.
As a quick aside, there are a very small handful of essential spells not mentioned yet, one that neutralizes poison for example, that are only in the campaign setting. If you don't mind filling these in then you should be okay.
You will also need to do something about classes though. Most standard D&D classes use slot based magic. Only the fighter, rogue, barbarian, and monk remain compatible if you completely change to an alternate magic system. That might be fine if you only like a small number of classes though. It has been argued in the past that D&D should have only had 3 classes, and with Sov Stone you could do it: Mage (Elemental & Void are basically the same class), Fighter, and Rogue. I think it's kind of nice to have more options though, as player's might feel that they are getting kind of straightjacketted, much as such a simple model might be nice in theory. The campaign book gives you a nice assortment of other classes to choose from, all of them without spells to cast. One of my big problems with core D&D is that everyone casts spells -- there's certainly nothing mysterious about magic for me when everyone uses it.
You could also scour together classes from other systems that you have -- the bushfighter, one of the noble/courtier type classes from Star Wars, Rokugan, etc. and maybe some other classes which don't cast spells pulled from various sources. That's definitely an option.
Quick Take:
Both books have about the same number of spells. With the codex you also get rules for creating spells and magic items. With the campaign setting you get some of the more basic spells and new mundance core classes. With both books there are some cool campaign setting based ideas to steal from as well. I guess you can choose which of those two factors is more important to you.