Hurry Up and Wait
Are you ready to tackle the new (old) world of Azeroth?! Well, chances are you are gonna have to wait until the furor dies down. The Blizzard Twitter feed and forums are blowing up with reports of servers down messages, 1+ hour queue times and many other issues. Some worlds are better than others but for now, it may be wise to wait til off peak hours.
Blizzard is aware of the issues and are currently working on them. Stay tuned for more updates are they flow in.