I just got back from the theater and while I thought it was pretty good it was definitely a mainstream horror film. It was often loud and was lacking in the kind of subtlety necessary to really make a film really scary. It had plenty of things I thought were just great (the television talking about how fun it was to play in the sewer when Bev gets home, the pictures if the ironworks explosion zooming in closer and closer, the first part of the slide show) and I was absolutely fine with the third act being crazy but the earlier stuff could have been dialed back some to make the later scares more effective.
Things I didn't like were the apocalyptic rock fight being played for laughs, Eddie's mother being played for laughs, Stan not having anything to do, and Mike not having anything to do. They pushed some of Stan's characterization onto Bill and it wasn't necessary. Stan's the one that has the idea to clean the bathroom because he is a clean and orderly person. He's got a rigid strength to him and it's why as an adult he decides to not go back to Derry. Being afraid he could handle but he just couldn't stand to be dirty. Stan's also the one that cuts everyone's palms in the book.
I don't understand why they introduced the Fire at the Black Spot but then also had it so Mike's parents died in a fire. It would have been so much cooler to have Mike's father or grandpa tell him the story of the Black Spot. Heck, you could have had it be a promotional thing where leading up to the film there's this 7-8 minute short where we get introduced to Mike and get that story. I think Alien Covenant did something like that?
Overall happy with it.