To be fair, most buyers
don't understand that 4 stars is bad - it was discussed on another thread i think, that in most cases, a 4 out of 5 would be deemed very good - just not by Ebay's standards.
If i have a good buying experience i leave the full 5 - but before i read some of the stuff on this forum i wouldn't have had clue that the sellers need an average of 4.8 or whatever it is to get their fees reduced. This is purely because, Ebay introduced this as an incentive for sellers - the sellers list more, they sell more and have more listing and FVF fees - brilliant they think, i'll get my discount, i've done everything right. BUT, Ebay purposely do not educate the buyer, so the buyer thinks, i'll give a 4, because to them, there's no difference - and some people actually just don't like giving full marks for anything!
In your case, i fail to understand why, with free shipping and the fact the items were sent out straight away they wouldn't have left 5 - but then who knows?! It was suggested that people (silly people) don't take into account shipping delays - i.e the item is sent out straight away but gets delayed at the PO (and how often that seems to happen!) and blames the seller....
Either way, the moral of the story is that once again, Ebay and Paypal win. You keep doing what you have to do to make it work for you. There's a suggested letter from another thread that could be included with a sale to inform the buyer (in a friendly, non-threatening way) how the stars affect you, and if they think they have had good service could they please leave 5 stars? Might be worth a look...