Every summer I buy a couple lots on eBay - one of children's DVDs, and one of normal DVDs. I'm completely buying them blind. There's no list of what's in the lot. Sometimes you can figure it out by pictures, but more often than not, those pictures are hard to see or don't zoom in. So you spend a fifth of your remaining AV budget and cross your fingers.
I've found that the majority of the DVDs that come are usable. I'm expecting to put 170 of the 179 on the shelves. (The others will be either too violent or too sexual.) I've never had one come that skipped or was damaged. And my patrons are thrilled to see new (to them) movies available. And I'm really happy to see DVDs taking up the space where the VHS tapes are now, to see those moving on.