British General says "Bring the boys back home"
When the commander of the army says it's time to pull the troops out, it's time to pull the troops out. And he's been saying so for nearly a year now:

General Dannatt, speaking on a visit to Afghanistan, did not repeat the statement he made in October last year that Britain should "get out [of Iraq] sometime soon", but the thrust of British military thinking is clear enough - the key campaign is now in Afghanistan, and anything that can reduce and even eliminate the British commitment in Iraq can help in that task.
"The army is certainly stretched. And when I say that we can't deploy any more battle groups at the present moment, that's because we're trying to get a reasonable balance of life for our people" he told the BBC.

Further down in the story is a choice anecdote that goes a long way to explaining why the British are leaving and the country is sliding further into the crapper:

The Sunday Telegraph reported that the senior British officer in Basra, General Jonathan Shaw, got short shift when he started lecturing American officers on counter-insurgency.
"It's insufferable, for Christ's sake," was the reported reaction of one senior figure closely involved in US military planning.
"He comes on and he lectures everybody in the room about how to do a counter-insurgency. The guys were just rolling their eyeballs. The notorious Northern Ireland came up again."'

Ahh, yes Northern Ireland, where the British Army found out that torture is counter-productive to defeating an insurgency and that negotiation works in the long run. I can see why the American officers would roll their eyes, after all the British have decades of experience fighting insurgents in Kenya, Ireland, Malaysia, Oman, and other assorted corners of the globe over the years, while the U.S. Army's experience with counter insurgency since World War II has been limited to the howling success of Vietnam and training and arming death squads in Central America (and CIA assistance to their friends the Taliban, but let's not bring that up) What could Tommy possible have to teach GI Joe?
As we used to say back in the Sault, "You can always tell an American, but you can't tell him much."
The British are right to pull out and redirect their efforts to Afghanistan. The U.S. will be trapped in Iraq for as long as they think they can still have "peace with honor" when fighting a native insurgency and will be stuck in the middle of a sectarian civil war. There are ways to win before the end of the 2012 election cycle, but they are brutal and will ensure the "terrorists follow us home" -- There is no happy ending for Iraq at this point. Even if the U.S. forces could go out tomorrow and by noon unerringly and without any collateral damage, put a bullet between the eyes of every single person in Iraq who has engaged in violence against the U.S. forces or other Iraqis -- basically the neo-con wet dream -- the insurgency would not be over. Because every brother, father, son, cousin, brother-in-law and friend of those now dead insurgents would be looking for pay back.
That is what is happening now as the U.S. forces go around kicking in doors, roughing up or arresting innocent Iraqis out of frustration or in error, calling in airstrikes that kill civilians, being there to be the target of car bombs that kill Iraqis. They are creating a nation of "martyred heroes" for Al-Quaida to put on their recruiting posters.
Partitioning the country might be a long range solution, but is likely to be a bloody disaster. I'd love to see the U.S. clean up its mess in Iraq, I just don't know how they will ever do it. I don't think that bell can be unrung. And the British are well advised to get out while the getting is good.