Hiya - while the park is officially opening to guests at midday today (2pm EST here), the official opening ceremony was held last night!
The video of the entire event has been posted here:
http://www.telegraph.co.uk/news/2016/06/15/watch-the-magical-shanghai-disney-opening-ceremony/
It looks spectacular and I can't wait to watch the whole thing when I get home tonight!
I'm assuming the park opening at midday to the public is so that all the staging can be taken down.