Both times we have been there (once we did a bus tour there and the other time we had a hire car and drove) we spent a full day there and still got back in time for a 7:30 dining reservation at one of the disney restaurants. I would recommend getting there for when it opens as by the time you have taken the bus tour, seen the imax and gone in the simulator it doesn't actually give you much time to look at the other things there.