Scary as hell.
Deeply, profoundly upsetting.

Coming from a family ravaged by mental illness, and being mentally ill myself, this was basically every anxiety nightmare about my Mom going crazy I have ever had.
The kind of representation I yearn for:
Harrowing displays of grief.
Catatonic shock and depression.
Disintegration of family units.
Brutal and visceral allegorical depictions of severe mental illness.

The kind of horror movie I have wanted for years. Formalist, Psychological, Conceptual, Metatextual and absolutely fucking terrifying.

A natural progression of Kubrick, Haneke and Carpenter. The presentation is clever without being overly so. The thematic conceits behind the stylistic quirks are justified by the text and elevate the film considerably. Acting across the board is stellar but obviously Toni Collette stands above the rest, delivering an absolutely earth shattering performance.

What criticisms I have are minor. Mostly I think the pacing is a little wonky in the first half and I think the ending could honestly have spiraled even further into hellish chaos. But the restraint is appreciated and understandable. The mundanity of the whole thing really helps sell it all as relatable.

I think comparisons to The Exorcist are valid. While entirely different films I think the cultural impact they will have in the long run will feel similar. I think this will become THE standard bearer for so called Art House horror. This comparison will unfairly hobble imitators but it would seem the bar has simply been raised.