Here's an e-mail I got from Universal:
In order to qualify for early entry you must have purchased your tickets
through AAA, ACS, CAA, Universal Studios Vacations, or have a
Star/Adventurer, SilverStar, Flex, annual, seasonal, or Celebrity pass. If
you are staying at the Hard Rock or Portofino Bay hotel you also qualify for
early entry.
Early entry days are as follows:
Universal Studios Sundays and Thursdays
Islands of Adventure Mondays and Wednesdays
Early admission time is 8:00am.