I have close to 500 transactions on eBay under my belt (Member since: Saturday, Aug 21, 1999)... mostly as a buyer. I have had few bad experiences and by pure luck have all positive feedback. The bad experiences I've had mostly were in the role as seller; typically, as in your case, with some bonehead that has little feedback. Here are two things to consider:

1)many sellers reserve the right not to sell an item unless the buyer has, say 10, positive transactions under their belt... chances are if they get through ten ok they are probably legit.

2)as a buyer I always look at the whole picture regarding feedback. Like you, I have learned that you can't please everyone and even worse some people are just plain nuts...

Don't sweat the small stuff... most people get the bigger picture.