Horror creatures work best when kept in the shadows, or not seen at all. This is where the film falls down. Pennywise is shown in broad daylight, with no subtlety or sense of dread. The other nasties are also pretty unoriginal, too. I felt like I’d seen them before in other films.
IT works best when it focuses on its human characters. The interaction between the kids is great, with some real touching moments that are up there with Kings best. But when you see a clown standing in the background waving a severed arm about... it loses all seriousness and the sense of uneasiness it’s trying to build up. Even the opening scene drops the ball, showing too much of pennywise and his frankly ridiculous CGI teeth.
Rent it before you decide to buy.