Feedback is a very important tool within eBay for both buyers and sellers to gauge their trading partners quality of service.  Posting  feedback should not be taken lightly and requires thought on the overall transaction.  My experience  (both as a Seller and as a Buyer) with eBay and the feedback system has been pretty vast which brings me to address several issues and problems about this process.  Please understand these are my personal opinions and would be open to discuss these.  I feel these should be used as a guideline as every case is different!

#1 Q .  Should Sellers Leave Feedback Upon Satisfactory Payment from the Buyer?     A:     If Sellers were to automatically post  positive feedback at time of payment, it leaves them unable to adjust that rating for anything that may occur after the payment is received.  I, for one, can think of any number of things from that point on that would influence that rating to be neutral or even negative. 
           
#2  Q:   When should a Buyer leave feedback for the Seller?   A:   This should be the first feedback to be exchanged between the buyer and seller as it is the Sellers responsibility to ensure the Buyer is satisfied with the entire transaction.  Once the buyer has received the item and it meets their expectations, the seller should be rewarded with receiving a positive rating.  If it is determined there is an issue the buyer can then take it up with the seller and delay the posting until the seller has addressed the issue.

#3  Q:   When should Negative feedback be given to Seller?  A:  Negative feedback should be the very last measure in resolving a problem with the Seller.  If there is a problem, the buyer should immediately take it up with the seller directly.  If there is no agreement made to remedy the situation then the buyer has the option of filing disputes/complaints with either eBay or Paypal at which time it is up to an independent 3rd party to decide the outcome.  An item arriving broken in and of itself should not warrant the seller receiving a bad rating as it does happen that the post office breaks things in transit despite the absolute best packaging job.  When this has happened to me I observe how it was packaged, the condition of the carton and most importantly, whether or not the broken pieces are all inside the packaging material and/or the box (which they had better be) and whether the seller has any history of similar instances.  The buyer still should contact seller and inform them of the problem for any assistance they volunteer such as in filing an insurance claim (if insurance was purchased).  Uninsured items arriving broken is a huge problem and one the eBay environment seems to want to pin on the seller!  If an item never arrives after receiving a tracking number and the status of the shipment recognises the item was in transit, this should release the seller from any fault and not affect the rating the seller should receive as the seller did fulfill the responsibility of shipping the item. 

This Guide is in Progress and will be adding additional questions, comments and adjustments!! Thanks for Reading and Voting in the mean time!