It was a typical posession movie, very similar to The Exorcist. However, it did have very good visuals and a lot of referencing to the church and spirituality.
Something I enjoyed was the cloud of doubt that shadowed the film - was Emma posessed, or was she mentally unwell? The skepticism that's only natural to humans was very well represented in the movie. I also found the character roles, particularly the Sisters, to be consistent throughout.
The visual effects were on par- only when you know what to expect it does become a little cringey and overdone sometimes. You know, your average possessed person - crawling the walls, spewing blood and hissing obscenities.
My only major negative is the camera action. To create a sense of unease and suspense the camera is filmed shakily, and often becomes quite disorienting. I really don't recommend going in there with a stomach full of sweets to watch it lol.
The actual film as a whole was still quite a pleasant watch, I feel as though many of the negative reviews flowing around are coming out of pure preference and going in with high high expectations.
What I would say to you is, go watch it yourself and find out if you liked it. Don't listen to the naysayers and just go see it, the worst that'll happen is you had a boring 90 minutes.
Hopefully this review helps those thinking about seeing it!