I was one of the lucky few to get a preview on TOTT yesterday morning and then the Sanctuary yesterday afternoon. Just happened to be in the right place at the right time for TOTT, then once we had done that we were told Sanctuary would be open in the afternoon. Once we did the mazes we gave feedback to the management about what worked and what didn't, etc.
I won't post any reviews or spoilers of the mazes, not until the weekend when people have had chance to go on them. Plus we were the first group of public to go through them so there could quite well be changes made to both mazes.
We were informed that previews may take place today for the Carnival, however I haven't been on park, so have no idea if they did or not.
It is also the staff preview event tomorrow night, so i'm sure we will find out much more then!