I just bought one, so I'll let you know how it works out.
According to blizzard (quote below)
Blizzard Authenticator for use with your World of Warcraft account.
Protect your World of Warcraft account with industry leading account security - introducing the Blizzard Authenticator! The Blizzard Authenticator is designed as a supplemental authentication method for your World of Warcraft account, giving you the security of Two-Factor authentication. Each time you log in using the Blizzard Authenticator you are provided with a unique, one-time use password to use in addition to your regular password. Log in with both and you can rest easy knowing that your account is now even more secure from malicious attacks such as keyloggers and trojans.
Once you have purchased the Blizzard Authenticator you can login to World of Warcraft Account Management to attach the token to your account.
Blue post : Onyxia's Attunement Removed on Beta
Quote: The attunement requirements for Onyxia's Lair have been lifted. The Alliance quests had to be removed due to King Wrynn's return. As I said in the quest forum, we'll try and come back to this one and adjust the questline to work with the current timeline. That won't happen for launch.
A shame in a way, the most "difficult" attunement still in the game being removed. But, it's got a positive side as well, you can drag your alts trough there for some quick loot now. I presume this will become a "feat of strength". (Achievement)