Yudkowsky's contribution is pedagogical rather than anything fundamentally new. He explains quite well in short the process of "decoherence" and links it well to the many worlds interpretation. He makes a case for why the "many worlds interpretation" is not really an "interpretation", but is just stating what the mathematics says on its face anyway .. and hence is the one we should adopt. In particular, he does a good job of connecting this to "timeless physics" - i.e. the Weyl equation for the "wavefunction of the universe" which does not have time in it.