I was disappointed precisely because I do believe he is a good man and wants to do what is best. I too thought he was destined to be president some day. He would have been a candidate I would want to vote for.
Many times we learn more from failure than success. I say in this instance, Powell has learned a great deal and could be a better leader because of it.
In the end, his mistake was following and not being a leader when he should have been.