After reading pauldonnelluk's comments about feedback I took a look at my own process of leaving feedback. I do wait until the buyer has left feedback before I leave theirs.
I am a seller with a 531 score at 100% positive. I take great pride in this score and will do my best to ensure that any buyers who are not happy with their purchase leave the transaction with a posative attitude to not just me as a seller, but to ebay.
The problem I have come accross on many occassions is this.
I list my items very fairly and honestly. I sell mainly minature silver stamps and on the listing I always state clearly in either a font 12 or 14 the size of the stamps and this information has its own paragraph that is put in the centre of the listing. People do not read the listings and then wait until the item arrives to complain about it. I am as fair as I can be and if I list the item incorrectly I will refund, if the item goes missing, even though I have proof of purchase I will refund.
If I left feedback immediately following payment - the people who do not read the listing and then are not happy with their purchase would leave me negative feedback, yet, as a seller I have done everthing possible to be honest and complete my side of the deal as best as possible.
I have been in the situation as a buyer when things like postal costs have been huge and I have contacted sellers to complain who have told me in no uncertain terms that if I leave them negative they will do the same for me. And, as pauldonnelluk rightly said, you either bite the bullet or keep quiet in the hope of maintaining your 100% positive score.
Please bear in mind that some as well as buyers, some sellers are very honest and would do anything to keep their 100% score.