These two aren't really spoilers, but great news:
There's an article on collider providing several story details on the movie, some of which are spoilers if you don't want to know how this differs from the book
This movie is very R-rated. Despite the fact that violence towards children can be a no-go with the MPAA, the creative team didn’t have to hold back. The studio wanted the film to be R and that was the plan before the Muschiettis even came on board.
Fukunaga's version is sounding worse and worse.
The biggest difference between this script and Cary Fukunaga’s version in the emphasis on the shape-shifting nature of the entity in IT. “It was a good script, in terms of characters and the depth of characters and such, but it didn’t really tap into one of the most attractive traits of the character, which was the shapeshifting qualities.”