I have heard various assessments re the effect of this move. This one, from Crooked Timber, is one of the more optimistic:
As Brad Plumer explains here, the regulations will transform the Congressional debate over bills to introduce a national cap-and-trade system. In the absence of EPA regulations, and assuming continuation of current practices regarding the filibuster, the Republicans in the Senate could block any action as long as they could muster 41 votes (and of course, ratification of a treaty like Kyoto requires 66 out of 100 votes). But now the effect of a filibuster will be to leave the EPA to deal with the issue by regulation, which might include establishment of emissions trading schemes, as well as technological mandates to adopt best practice technology. Almost certainly, some Senate Republicans will prefer a deal where they get to protect some favored interests to a system of regulation over which they have no say.