From the You Can't Really Please 'Em department. Think about this: A certain portion of the world population both wants the U.S. to pull out of Iraq immediately because the U.N. hadn't given approval to invade, and also thinks the U.S. needs to stay to clean up the mess our country made there before we leave.
Can't have it both ways. Now, those aren't the only two options, but that's about the sum total of the left criticism of the war. My personal opinion is to stay long enough that a legitimate government is established. Not until Iraq is secure and friendly. Basically until a consitution is written and we no longer have an interim government. (And contrary to what some people think, the currently planned elections are actually for a second interim government.)