I share your positive sentiments, but would argue that he was always united with the president. He didn't say one thing that was not the wishes of this president. It is the job of Secretary of State to hold the door open for diplomacy until all hope has faded, not to make war. War is Rummy's job. We need both a Rummy and a Powell.
Iraq is full of people who hate each other. Sometimes miracles happen and people can unite over the victory of a common enemy they all hate, but when they sit down tomorrow and try to actually figure out what to do next, it will not be smooth. They will need a mediator of incredible skill to work this out. Prayers for Colin Powell are needed now. I am glad he is with us (just try to imagine his predecessor).