I know that the issue of feedback is now debatable. Whether there is any point to it now sellers can't leave negative. Buyers can be trigger happy when negging now they know they're safe from retaliation, but what alot of buyers don't know is the importance of the DSRs (Detailed Star Ratings).
Ebay tells a buyer that a 3 is ok. That a 4 is satisfied, That a 5 is very satisfied. So it's ok to mark a seller all 3s, or all 4s isn't it? If a sellers average goes below 4.6 (at time of writing but I believe it may change) they can actually have restritions placed on their account, this can be devastating for someone who makes a living/partial living on ebay. For someone who doesn't sell much, to have someone mark them 3s and 4s makes a huge difference.
Also, there is the issue of the dispatch star. This December I saw my rating go down, I go to the Post Office every business working day, including Saturdays, this didn't change through out December, but things got held up in the Christmas post. Customers don't seem to realise that dispatch time and postage time are a different thing.
Now the P&P star. When I buy, I always look at the stamp price of the parcel, then I add on what I think is fair for PACKAGING, then I mark accordingly, buyers need to be aware that P&P includes packaging.
Ebay need to make these things clearer, as they tell one thing to the buyer then another to the seller!