Just got back from the film. Here's my quick breakdown of the positives and negatives without spoilers.
Pros: Cage is great for the time he's in the film. Great cinematography if you're into visual flare and style. Some decent elements of horror that are very interesting.
Cons: Hardly any visceral horror or gore whatsoever, feels incredibly "safe" for a film like this. Story is really competent and well-written until the very last act of the film and feels like a cliched trope we've seen in too many horror films in the last few years.
Overall, you'll have a good time. It's got moments of pure horror that can be easily expanded on or brought to light more, but the story itself takes a massive nosedive that just felt really jarring and too on the nose as if the audience wasn't intelligent enough to figure it out themselves. Just felt too safe to me to be considered the horror film of the year. There are significantly far better horror films that easily can make Longlegs run for its money and honestly the hype glorified this too much to be enjoyed as it set out to be. It's got great moments that show the potential of what it could have been, but it just detoured into something that everyone has seen already.