Leave appropriate feed back, period. The entire purpose of this system is to build a reputation. This way, we can avoid shady members. You could have avoided this seller if everyone else who had had bad experiences also left negative feedback.
By keeping silent, you are allowing this seller to get away with poor service. Your own reputation will speak for itself. If you have 50 great reviews, and one bad one, and it comes from a person with a low feedback score, who is more credible?
Plus, you can now respond to feedback given to you. So if he leaves a negative, explain your side and defend yourself.
Don't let this person get away scott free. Judging by the transaction details, he would merit a neutral mark.