250,000+ Copies sold!
200,000+ Accounts created!
100,000+ Concurrent players as of 5PM PST on the 23rd!

To meet the overwhelming demand Blizzard is setting up more servers (16 more as of today).

Read the Official Press Release here (http://www.blizzard.com/press/042427.shtml).
Read some relevant articles here (http://forums.worldofwarcraft.com/thread.aspx?fn=wow-general&t=23215&p=1&tmp=1#post23215) and over at WorldofWarcraft.com (http://www.worldofwarcraft.com/)

Feel free to join us on our forums (http://wow.forums.thedruidsgrove.org/).

Found this very interesting,
Blizzard Extends Free Trial
Ordinn posted on the official forums that they are going to extend the free trial people to make up for the problems they have been having. Here's the text of the post:

Since its release two and a half days ago, World of Warcraft has already seen incredible concurrency numbers across all active game servers. To keep up with the demand from our players, 47 new servers were made available, increasing the total number of servers to 88. Doubling our server capacity in such a short period of time created issues in existing servers. We immediately recognized the issues and began implementing fixes. However, some players were unable to log in and enjoy the game during this period.

We sincerely apologize for any inconvenience and are dedicated to providing World of Warcraft players with the best play experience possible. Therefore we'll be adding a small trial-period extension for players who created accounts before or during the downtime. In the days ahead, we'll provide additional details on how the trial-period extension will be determined. As always, we appreciate your continued patience and support; we're still monitoring the servers very closely and making adjustments as needed in order to ensure that World of Warcraft continues to run smoothly for everyone playing.