From the publisher's website:
It is time now to introduce you to the definitive incarnation of Burning Wheel, the Gold Edition. Burning Wheel Gold is contained in a single 600-page, hard cover volume. While it is the same game as BWC and BWR, Gold is also much more: It has been reedited and reconfigured to reflect nearly a decade of intensive playtesting. Every loose rule has been tightened down. Every missing piece has been carefully added. This is the game that we play at Burning Wheel Headquarters. We are the most proud of this book; it is the culmination of a lot of hard work and even harder play.
Here’s what you can expect from Burning Wheel Gold: The entire text has been reedited for clarity; skill obstacles have been included for every skill; all traits and skills have been compiled into one list; all lifepaths list their requirements; Duel of Wits and Range and Cover have been clarified; Fight positioning has been simplified; and each Fight action has been explained; Sorcery was tweaked to make it simpler and less loonie; low obstacle Faith tests have been added; the Mounted Combat rules have been reimagined (and made useful). Those are just the changes from the top of mind. There are more!