In 2002 we stayed at All star Movies- the safe was way too small for a laptop
in 2003 we stayed at CBR- again safe was too small...both times we took a lap tops and on both trips....I, commando in the morning, to get to the parks; forgot to close & lock the safes and both times we came back to the rooms and every penny was accounted for. Again as suggested, we put the laptop in the drawer or in a locked suitcase. So I would say yes, it'll be safe in the WDW hotel.
BTW- in 2004 we stayed off-site and the safe was big enough for the laptop and there was NO WAY I wouldn't have locked it up when we left.(definetly felt safe at WDW) But we also had 3 laptops between the 5 of us.