Best Buy's GCU kills buying used for me. A game is cheaper with the 20% off new games than the 10% off a cheaper used game, in lots of cases. That, and many of those newer games have $10 rewards when you pre-order, so new really ends up cheaper than used for me.
Unless I feel I've missed out on an older titles and there's a B2G1 free used sale, I pretty much just get new games at launch, then trade them in when I'm done.