Yes folks. You should be completely confident in Blizzard. I mean, the night before how many tens of thousands of people from around the world try to order tickets, the authentication servers go down. Many users are experiencing it, however a few are not.
What on Earth could go wrong tomorrow?
Reythur, a Blizzard blue poster, has said that the issue is being investigated. We'll update this post with more information as we get it.
Update #4: Things are working now it appears for all Battle.net accounts and all regular accounts.
Update: Reythur has confirmed the authentication servers are experiencing problems, but there is no ETA on things being fixed.
Update #2: There are some people for which things have been fixed, and others for which things are still broke. This is evident on the official forums, however nothing more from the blues.
Update #3: It appears that the authentication servers are only down for those who have not migrated to Battle.net.... there's no official confirmation of this, but we can confirm on staff there is a brightline here.