I have to say, my first reaction to seeing an added stress track for Soulfire was "Awesome!" but the more I think about it the less certain I get. Done right it I'm sure it can be superb, but I sure hope they haven't made Soulfire-users capable of casting _more_ spells per scene than non-users because I don't think we've seen Harry have more staying power with Soulfire than before, that's primarily a Winter Mantle thing...
About the general rules update, I don't get the feeling that it's really a 'rewrite'. A lot of the headlines in the ToC looks more along the line of essay-style 'here's how you can use it' rather than rule changes. "How Long Does My Effect Last", "Do You Even Need To Roll", "The Philosophy of the Elements", "Hexing".
Of course, there's definitely new rules in there! "Evocation and Simple Actions" has to be some small amount of new rules since Evo at the moment is only described as three of the four Conflict actions + Counterspell (which is sort of an attack against a spell rather than an active opponent). "Mental Toughness" is also definitely new stuff, but I don't think we have to fear a complete rewrite of the magic system.
