IMHO - 505 has zero ghosting (probably as the rest of readers with the new screen), 500 - has heavy ghosting although tolerable.
Then again, it depends on how you look at the issue. Have you ever read a delux edition of a book printed on india paper? That's what I call ghosting! So, we can say that PRS-500 is just a very exclusive version on a par with delux hardback editions printed on india paper (Bible paper)
