Just thought I would post an update about this promotion. It technically ended at the end of September, but I was told that we could still get the $200 trade-in value for our phones (3 iPhone 4 and 1 iPhone 5) as long as I had gotten a quote using their automated system and showed them the screenshot. Turns out that wasn't necessary, but they did check that we had bought new phones for each one being turned in. I was concerned that they might say some of them didn't qualify because we didn't get them direct from AT&T (their shipping times were ridiculous), but they didn't mention it.
It does seem like your milage may vary, as some places seem to be more strict than others about various components of the deal. I walked out with an $800 credit, which was pretty fantastic considering that everything but the iPhone 5 was a pretty low-end model that would have had little resale value.