Queues are the highest most of us have ever seen tonight. On my home server of Eldre'Thalas I was behind over 850 people at one point, and have had over an hour wait be estimated for me more often than not. I maxed out at 115 minutes.
The estimated wait time will fluctuate back and forth depending on the frequency in which players log off or leave the queue in frustration.
Perhaps the biggest thing we need to worry about this expansion is not server down time, but the phenomenal amount of players wanting to get in the game.
If Blizzard has any announcement about this, or solutions (other than transferring realms) we'll keep you updated here. Other than that... good luck getting in.