I know there's a lot of interest in BW here, so I thought I'd mention that the third edition of the Burning Wheel rules (called Burning Wheel Gold) comes out this summer.
It's purported to have major improvements in rule specificity , procedural clarity (especially with Duel of Wits), fight positioning, and revised sorcery rules, among other things. More info at:http://www.burningwheel.org/?p=276
According to Luke, it will 'not' be backwards compatible with the current 2nd edition (Burning Wheel Revised) rules, but it should be largely compatible with the other supplements (Magic Burner, Monster Burner) except on a few specific points (positioning, sorcery). He has talked about future 'upgraded' releases of those supplements, but hasn't promised yet.