Update: New Spires of Arak and Nagrand Maps added. Currently Horde is available.
Alliance causes a crash. In addition, new quest scenario where the Iron Horde attacks your Garrison.
Correction: @TheRedShirtGuy tells me Alliance is playable. If your character was in Shadowmoon last time, it might crash. Alliance now starts at Tanaan Jungles. Create a new character if you get crashes.
Update: When launching Warlords of Draenor for the first time, the player will get a new window highlighting some of the new expansion’s features.
Original post: World of Warcraft: Warlords of Draenor Alpha build 18471 currently downloading (July 25, 11:00pm EST). No ETA on servers going online. Stay tuned for patch notes when they become available.