FYI, leaving positive feedback for a buyer immediately after receiving payment is, unfortunately, not the best way to go either. sometimes the transaction will go to pot after the buyer has received the item, and you'll still want that ability to leave a negative feedback if it does.
one example: the high-maintenance buyers who don't read the listing, and get all cheesed off and petulant (and leave negative feedback) simply because they didn't read the part of your listing that said, "item doesn't work, sold for parts only".
there are a lot of idiots out there who love to scream, and a good chuck of them seem to be on ebay. my interactions with ebay are mostly from the buyer's perspective, but i do sell from time to time. and being a responsible seller is a pain in the @$$, in part due to the problem buyers.