Plot: This might be the most regimented season of the show. There are very specific turning points, which — for once — help the season stay on track. The narrative style is new and refreshing. It's satisfying to see a show within a show, then to pull out into the "reality" that still exists in the AHS universe. In the end, though, there's a lot of confusion with the "real life" characters and their "onscreen" counterparts. We spend way too long in the My Roanoke Nightmare portion, especially since the real scares come with the reality that lies beyond. There's a better attempt at pacing, but it still misses the mark.
Ending: With such a fixed structure, we do get a pretty solid conclusion to the show. We see the first part, a five-episode stretch called My Roanoke Nightmare, to get the original story. The second, Return to Roanoke, runs its course in three episodes. Then, we get an episode to wrap up. Lee sacrifices herself so her daughter can go free. The question is, does it really pay off? Since we get to see so little of the "real" Lee and must reconcile with all the various "real" and "fake" versions of characters, the final impact isn't so strong.
Scariness: I'll reiterate that Roanoke spends way too long in its first phase. Since we know it's a manufactured TV show, there are no stakes. The ghosts aren't scary and the tension is absent. This could have easily been three episodes instead of five. What I will say, though, is that the actual spirits in Return to Roanoke (episodes six through nine) are terrifying. That's the true horror of the season, and I wish we got to live in it longer. We didn't.