I am not a fan of ebays new system, but the old system was being abused by sellers.
I purchased some cell phone accessories from some guy. Three weeks after I paid I email him asking where they were, a week later I get an email from him claiming that they came back undeliverable and that I needed to verify my address or he would refuse to "resend" the items. I told him the address was correct and he "sent again" and it showed up after another week. The package did not have any signs of being sent more then once and there were at least 4 other people who gave him feedback mentioning the "undeliverable" comment. Now here is why he was abusing the feedback.
2 of those 4 people left neutral feedback stating the issue, one left possitive, but still stated the problem, one left negative feedback. All four of those users were given negative feedback by the seller with the comment "left incorrect feedback, never deal with this buyer".
I think that it was totally unfair for a seller with 3k feedback (and a growing number of negative feedback) to be blaming the buyers for his mistake and/or his not having the product he advertised.
Were a few sellers ruining it for the masses, you bet. But from ebays point of view, for every sellers that leaves, another two will come. While if you loose the buyers everyone (esp Ebay) suffers.