As an experienced seller of many years and feedbacks, I still occasionally receive bad feedback from buyers claiming that the item they received was 'not new', despite being described as such.These complaints are almost invariably from non-UK customers, and usually US buyers.
It is important to realise that for environmental reasons (ie avoiding clogging landfill sites with pointless plastic shrinkwrap), most UK issued CDs are not sealed at point of manufacture. You will notice this in UK CD stores as well as online.
If a seller has a huge positive feedback, it is usually fair to assume that they are not in the business of 'ripping off' their customers. Therefore if they describe an item as 'new', it will be in mint, unplayed condition with no surface marks or damage to the inlays or casing.
A small footnote regarding 'sealed' items -- I have in the past discovered sealed items with no disc or the wrong disc inside (presumably an error in the factory), and on a recent trip to NYC, I found a CD store selling used CDs -- in shrinkwrap!
The moral of the story is that when you buy goods from another country, you cannot necessarily expect exactly the same product as at home. E:Bay now gives the option for a UK seller to list a CD either as 'New' or 'New and Sealed'. I would advise both buyers and sellers to take advantage of this feature and avoid any feedback unpleasantness.