The Shia get an acknowledgment that Islam is "the official religion of the state," just as the Church of England is the official church of that state -- though, unlike the Anglican bishops, Iraq's imams won't get permanent seats in the national legislature.
The Kurds get a loose federal structure in which just about everything except national defense and foreign policy is reserved to regions and provinces. I said in the week after Baghdad fell that the Kurds would settle for being Quebec to Iraq's Canada, and so they have.
The Sunnis, who ran Iraq from their days as Britain's colonial managing class right up to the toppling of Saddam, don't like the federal structure, not least because it's the Kurds and Shia who have the bulk of the oil. So they've been wooed with an arrangement whereby the country's oil revenue will be divided at a national level on a per-capita basis.
If you'd been asked in 2003 to devise an ideal constitution for Iraq's very non-ideal circumstances, it would look something like this: a highly decentralized federation that accepts the reality that Iraq is a Muslim nation but reserves political power for elected legislators -- and divides the oil revenue fairly.
And if it doesn't work? Well, that's what the Sunnis are twitchy about. If Baathist dead-enders and imported Islamonuts from Saudi and Syria want to make Iraq ungovernable, the country will dissolve into a democratic Kurdistan, a democratic Shiastan, and a moribund Sunni squat in the middle. And, in the grander scheme of things, that wouldn't be so terrible either.
To be sure, we shouldda done this, and we shouldda done that. Yet nonetheless Iraq advances day by day. The real quagmire is at home, where the kinkily gleeful relish of defeatism manifested by Cindy Sheehan, Joan Baez, Ted Kennedy et al. bears less and less relationship to anything happening over there. Iraq's future is a matter for the Iraqis now -- which, given the U.S. media, Democrat blowhards like Joe Biden and Republican squishes like Chuck Hagel, is just as well.