I believe this past Monday was its first official day for the guests. As far as a grand opening, I have no idea when that might take place.
I went on it yesterday for the first time. It was cute, but the wait took forever. We got right inside the building but ended up waiting 35 minutes in line. I've heard of other waits that have been over an hour, and I can't imagine waiting that long for it. The area for the queue inside was just a wee bit too dark and humid which made it a bit uncomfortable.