I understand your point, but that's not the way I handle the feedback. I don't consider the transaction complete until the buyer has received the item and is happy or has notified me of a problem and what they would like for a resolution.
When I am the seller, I leave feedback after the buyer has notified me they have received the item and are happy with it. In my opinion, the buyer has not held up his end of the bargain just by paying for the item...too many things can go wrong after the payment is made. IE buyer refuses insurance, than leaves negative feedback when the postal service loses the package. Depending on how I feel about a buyer that pays with paypal, I may wait a couple months before leaving feedback to insure I can reflect a Paypal chargeback in the feedback if necessary.
As a buyer, I will either leave feedback or contact the seller if I have issues when I receive the item.
My .02, but
