8/10 for me
Once again Steven King should demand royalties from Mike Flanagan. Just as Hill House heavily borrowed elements from The Shining this series is a riff on Salem's Lot. Thrown in are a few other King-isms lifted from books such as The Mist and Storm of the Century.
Don't get me wrong. My wife and I really enjoyed this series.
Where it fell short was mostly in production values. There is a lot of sub-par CGI/green screening that distracted from the drama.
e.g. In some of the boat scenes the side lighting is clearly coming from studio lights. When Riley takes Erin out on the water for their last time together the background water at some angles is this undulating mass of random waves with no discernable direction or wind to drive it. It looks more like computer generated "noise" of some sort.
e.g. In her first appearance the aged Mildred is clearly a younger actress wearing "old person" makeup. I guessed right then that her getting younger was going to somehow figure into the story.
I agree too with those who commented on the tendency of characters to launch into monologues that went overboard with the verbosity and eloquence. The worst example of this for me is when Sheriff Hassan gives us an overly long and emotional back story to explain why he won't investigate (shut down?) the Christian church.
On the other hand, I did like Riley Flynn's poetic description of what happens when we die. Even if death means the complete and total end of us those final minutes will be heavenly enough. I like that thought.
Sidebar: The monologues are another King-ism... the flawed characters in his books often talk - or think - like this at critical points in the story, usually to show us how noble they are in the face of adversity.
Finally... is a sequel in the works? This story ends conclusively enough for a limited series, but leaves enough wiggle room to carry on the story.