WoWDB

If you want to see what it changes your model to, go to Lich King and click View in 3D.  The duration lasts 20 minutes but does not persist through death.  The item cannot be used in arenas.

edit: the mess up of the content of my post is a bug on wowdb's end. when it is fixed and if i forget to come back to edit out this note, please let a moderator know so they can do it for me.

Heh.  FlyingKick is my favorite; such a derp face. X)

Some notes:

• You cannot mount nor take a taxi while shapeshifted in this form. This has since been changed in an Oct. 30th hotfix. This is still not corrected.
• It does not display  Frostmourne. Your own weapon(s) will be shown instead.
• You can engage in combat and take damage without losing the appearance.
• Using the following emotes will use both your racial version and the human male version at the same time:
• Laugh, chicken, cry, kiss
• The costume will not be overridden by other appearance effects.

Any item with charges that is available from the vendor is bugged. The tooltip will show only "1 charge", but it will display the proper amount once purchased.

Edit:  This was in response to a different comment which has since been deleted.

Whomever took the screenshot of the Arthas costume in front of the Lordaeron throne... you cheeky person you. /lol

I'm glad you approve. ;)