Just a couple notes, and a reference to this original article that explains how it works from a year ago:
First Look at iTunes Digital Copy – Macworld
http://www.macworld.com/article/131751/2008/01/digitalcopy.html
I had no reason to use this until a little over a month ago, I bought Wall-E and was anxious to try the Digital Copy feature. I put the special third disc in my MacBook, which already had iTunes running, and it would bring up the authorization box off of the disc in the finder, but the authorization process kept timing out. So I found that by closing iTunes, and having it be opened by the authorization program at the appropriate time, everything worked.
Just an FYI in case you are encountering frustration with the activation.
Kottke, via Daring Fireball. The “format 22″ is really very sharp.