one time i ordered from amiami.com EMS shipping and for some reason it was taking longer than was expected (10 days?) so i called up Auspost and they said the package was actually on its way to being sent back!
they enquired further and apparently the person who had mailed it had wrote my address very badly so they didn't know where to deliver it. they had to call it back in and fix the address to me and then i got it 2 days later.
informed amiami about how unhappy i was with it and they ended up refunding my postage costs.
tips :
if you feel like there's something wrong with what a seller is telling you, than it most likely is. so do what you must to get the proper tracking info.
once tracking info has been provided, delivery is out of the hands of the seller, so be sure to remember that and if there's a delay, phone up auspost and ask them.
always be aware of how many days you have to file a dispute.
only pay with paypal for ebay and only ebay. paypal will do nothing to get your money back from anything other than ebay - this is from experience.