I bought the 20 the last time this was offered and I only had 3 discs work straight out of the envelope. However, I took them to be resurfaced at Game Crazy and ended up with 18 of the 21 discs working (I got 21 because one of the games was DMC 2). It ran me $10 to get them resurfaced but it was still a pretty good deal.
I would say dont go into this with really high hopes. Part of what you are paying for with any grab bag is the excitement of the draw.
"I was perfect..."