Upon patching and opening up WoW today, many players were greeted with the only marginally helpful message "Your video settings have changed." The first question that leapt to my mind when I saw it was "what settings, and why?" It would have been nice to tell us that, I think.
Fortunately, Bornakk knows (I sometimes suspect he knows everything, with that manly beard of his). The answer is that the Projected Textures option, in Video Effects, now defaults to on. I assume players that had it turned off - like myself - had it turned on for us. What the option does is display things like the rune circles for Blizzard and Rain of Fire, which many players were confused to find disappear when patch 3.1 hit. So if you're wondering what the change was, or wondering why you suddenly see spell details that you didn't before, now you know.