If you pre-purchase your AP, you get a voucher with numbers on it that allow you to get into the AP section of the WDW website (there's a "button" toward the top right of the site on one of the bars). It can be a little odd figuring out how to put in the number, but it does give you access to a little addt'l info. The date for the AP use doesn't start until you get the actual AP at Guest Relations (if you have some non-Park time to kill at the beginning of your trip, you can get the AP and TIW at GR at DTD (near, or at?, World of Disney).