I love paypal as it allows me to buy from the US and not have to pay the outrageous fee the po charges for US money orders. The last time I did that the fees were more than the value of the money order. I don't need an invoice and have only had a problem once when the seller had a typo in her email address (I copy and paste to make sure I get it right). I like that the seller gets the money right away and doesn't have to wait for our slow po to get it to them.