Word of Warning:
I recently purchased:
Mario Power Tennis
NCAA Basketball 09
during the Gamefly under $10 sale last week.
All the games came with mint boxes/manuals... but the disc quality is terrible. Smudges all over the label side and scratches all over the underside. Mario Power Tennis was scratched the worst - with visible chips of plastic missing - all along the outside - but it still works. Prior to my purchase, I had read that Gamefly used games where "near pristine" but that was hardly my experience.
Edit: When you think about it, how on earth could games that have been through so many mailings/handlers be near pristine? I'm sure these games are some of the "most played" used games you can buy.
I am sure it also matters on whether or not you are buying PS3 or 360 games. I have bought several PS3 games and all are mint. Blue Ray helps I am sure, but I bet it also has to do with the fact that there are more people playing 360 games.