Oh also, just in case it hasn't been noted or if anyone isn't in the know yet, Gamestop is no longer taking trade ins for:

XBL Vision Cams. Due to there being the Kinect now according to the worker.
Memory Cards. Assuming because they aren't compatible with the Slims.
Official Xbox Wired Headset. I'm stumped on this one, they still sell them new and have a moderate stock of them...