• Broad coverage. They've proposed coverage for just about all electricity-related emissions for the region -- even if the generators aren't in the WCI. That's a big deal, since it helps to ensure that we don't "comply" with emissions limits by importing dirty power from a part of the world with no climate cap.
• Limits "contract shuffling" loopholes. Contract shuffling is like rearranging the deck chairs on the Titanic: it's a way for electricity providers to "comply" with climate obligations by rearranging power-supply contracts. By shuffling contracts, "clean" power gets shipped into the WCI and "dirty" power goes to states with no cap -- but the only thing that actually changes in the real world is signatures on a few pieces of paper. Of course, it's hard to stop all contract shuffling, since a lot of it is beyond any one state's control, particularly if the generators are in other states. But the WCI proposal takes one big step forward: it would prevent high-carbon generators in the WCI from shipping power outside the region in exchange for "clean" power generated elsewhere.
• Plays well with others. The system they've outlined would segue nicely into a national cap-and-trade system. They're not going to create a separate, incompatible system for the western U.S. that is hard to integrate with the rest of the country. That's a huge win, since it could make designing a comprehensive, national or North American emissions system a lot easier down the road.
• As simple as possible, and no simpler. Administratively, it looks like this system is about as streamlined as you can get, while still ensuring that the bulk of electricity emissions are covered by a hard cap. And even better, the system is actually set up to get simpler over time, as more states in the western U.S. and Canada develop their own emissions limits.

Astonishingly, the WCI proposal seems to be making some of the electric utilities stand up and cheer, too. That's quite an accomplishment -- a proposal that makes at least some utilities and most climate advocates happy, all at once.

So my hat's off to all of the folks who worked on this -- it's a big step forward. Let's hope it portends more great stuff on all the other issues they're wrestling with ...