As for the TV series of The Exorcist, the funny thing is that I've seen these five episodes before, when they first aired, more than half a decade ago. I stopped then, got busy and failed to get back to the series.
My impressions then was that it felt sort of post-Hannibal: artful TV horror that thankfully wasn't quite elevated horror but also not as comic-book fun like, say, Supernatural or even the at-time campy Hannibal.
I felt that the lofty themes of faith and community matched with body secretions of all sorts was a better callback to the 1977 #film, rather than some other little moments and bits of dialogue. I wasn't sure at first what to think about the lore it was introducing (Church conspiracies, new twists to its demonology), but I did grow to like that. I also thought that--and this may offend purists--but the use of Chicago as a setting is better than the use of DC in the film.
Because of the smart way it was (as the credits state) "inspired by the William Peter Blatty novel," episode 5 was quite a turning point for me. Part of the reason I stopped then AND now is that I'm not sure what to think about what just happened.
Much of the great build-up in the first four episodes reaches a climax here, and it's mostly effective and feels like a mid-season cliffhanger. Again though and even more than the halfway point of The Peripheral, it's such a different approach that I literally had to stop and take stock.
Atmosphere and implication were pretty much the norm in the first few episodes alongside character building, and even several cliche but effective startles and funny/eerie nightmare scenes don't detract from the subtlety and sophistication.
Episode 5 directly confronts us with plot events and revelations. The former generally work well, although one makes me roll my eyeballs and isn't very convincing, except as an attempt to be shocking about the secret lives of priests that doesn't quite fly. The revelation, however, is a major plot twist. It's one that's executed extremely well, ESPECIALLY once the viewer realises what's coming. It's textbook perfection dramatic irony, as the characters wait for the unfolding of what viewers already know.
Like all such plot twists, it forces you to rethink everything you've seen so far and also makes you think about how they'll follow it up. I don't have too much of a problem with the former, since the plot twist remains plausible. However, it's a plot twist that they could have chosen not to use, and so that makes me worry about where the series will go from here. And it could turn out to be a really bad decision, and I'll need to prepare myself for that possibility, in case the series squanders what greatness it had in its first four and most of the fifth episodes.
BTW, I grew up Catholic and am now "almost-lapsed," but the first film always stays the prime example of pop culture theology. I never read the book though and have never felt, er, compelled to do so.