Remember when Blizzard said that you couldn't use flying mounts in Azeroth? Well, out of respect for Blizzard, everyone has accepted this decision and no one has tried to fly in Azeroth.
Just my little joke. Of COURSE someone's figured out a way to fly in Azeroth, although it requires a certain class and spec. A group of beast mastery hunters have discovered that if you spec a couple points into Animal Handler, you won't get dismounted when you fly through portals. Through this method, Chozo of my home server Magtheridon and some others have been spotted flying in Orgrimmar, Dustwallow Marsh, the Blasted Lands, and other areas.
I talked briefly with Chozo in-game. He said that while he'd spent some time hanging out in Orgrimmar with his wyvern, he hadn't gotten to explore the world much because he kept getting dismounted by invisible air packets. He was considering trying to get summoned to interesting areas, but most of his guildmates were busy with leveling and instances and he didn't want to interrupt them.
Other hunters who respecced to try this out reported the same dismounting problem, so I wouldn't go dropping Marksmanship just yet. Still, expect Blizzard to fix this before some hunter gets lucky and discovers GM Island.