Completely depends. I've only had one book that was awful quality (i actually just bought it last week). It was so bad (typos EVERYWHERE) I complained to Amazon and they told me if I wanted a refund they would refund me.
I need the text for school so I might wait till I finish reading it for my class and if there is no update get a refund.
Knowing that Amazon is willing to refund poorly formated/copied books makes it easier for me to buy more even if I had one bad experience!