Like Sienna said, you get free admission on your birthday.
From all the ad campaigns, it seems to me like basically it's just a "filler-year" where they're saying, "Come here to celebrate your anniversary/graduation/birthday/winning your first baseball game!". That kind of deal.
I'm sure others after me will have more info, but if I'm not mistaken they're also having a new "Celebrate" parade that will replace the Parade of Dreams.