changed the amount of XP earned... at level 70.
But wait, you say, we don't earn XP at level 70! Ah, but we do -- after you hit 70, you actually continue to earn XP to level 71, but you never actually ding. And while before the patch, the amount you had to earn to "hit" 71 was about 814,700, now it's up to 1,256,500. Which makes sense -- while some folks are saying this might have been done to just fix a bug, Boubouille says it lines right up to the difference between vanilla WoW and the Burning Crusade, which means we'll need to earn about 50% more XP per level in Wrath of the Lich King.
Of course, this affects a few other things in the game -- Mania notes that pet loyalty is based on percentage level XP earned, so Hunters at level 70 will now need to hang out with their pets for longer to earn a higher loyalty level. But Blizzard isn't nerfing anything here -- from what we can tell, they're just lining up level 70 to become the first level of the next expansion instead of the last level in the game.