when i sell something, i usually wait until i see confirmation that the item arrived before i leave feedback. i dont think it makes much difference, but i would at least like to know that UPS/USPS did their part before the buyer claims the item never arrived.
im not sure if you can still do this, but i think the seller can respond to negative feedback, and it will show in your feedback section.
ive had more good experiences than bad with ebay. i HATE when the buyers dont pay though. why bother bidding?