I liked the episode, I felt it was pretty average with some other mlp episodes. I loved that little gag where Applejack put all those helmets on Applebloom (double helmets!). One thing that really bothered me was that Applejack felt a little out of character, they seemed to have exaggerated the whole "I won't let my family be harmed by anything" aspect of Applejack. Besides that, the episode was well executed and had fun little bits of world-building and a new creature.
I'm starting to wonder if Applebloom actually went to Tarturus, if that's true, then that would be awesome!