I have my own simple solution...
I never leave feedback - period. I just don't have time to massage some sellers or buyers ego. If I got screwed on a deal I guess I would leave negative feedback but that hasn't happened more than a few times in 10 years on Ebay. Sadly once my Paypal account drys up I don't think I will do anything on Ebay since I am not going to accept credit cards (and pay the fees) no matter what they say.