Well, if you have an MSDN or Technet subscription, you can. Otherwise,
you'll need to use the "test drive" http://office.microsoft.com/en-us/products/HA101687261033.aspx or wait until
it's available for purchase, which is later this year for volume-license
customers (businesses) or early next year for retail (individual) users.
The beta preview versions that were available for download a few weeks ago
are no longer available.
