Intellectual honesty
If, and it's a bit IF, Iraq develops into a healthy tolerant democracy long after we are gone, then some reassessment of the war's worthiness would be in order. The measure would be if that social progress in Iraq was worth the lives of (currently) 4500+ Americans.
Regardless, there is no forgiving the arrogance of Rumsfeld, and the idiocy of Bush, for not changing strategies on the ground YEARS sooner.