For one thing, I LOVE the animation! It just keeps getting better with more expressions, more motions, just overall more stuff going on that I really like out of this show! Even though I was a bit annoyed with the cliched dialogue and plotpoints, I just loved seeing the ponies move, and also talk! I STILL love the voice actors of this show, and still remains one of the best aspects about the show and one of the key reasons why I watch it to begin with!
Other stuff I liked... that "bee stare" at the beginning was pretty funny, as was Pinkie's ramblings. That beekeeper looks a lot like the mailpony from The Last Roundup, doesn't it? I liked Fluttershy in this episode, but I always like her. I liked those spider things, even though they don't factor that much into the story, and only get a throw-away line and are only seen at the beginning. The old castle looks cool, though I do find it strange that such a castle that use to be the home of Celestia and Luna had a lot of strange decor, but I'll get to that momentarily. I like that Angel wasn't a total twat (forgive my French) this time around. I liked how when Applejack said "nopony knoooooooows", it mirrors the "oooooo" she made in Look Before Your Sleep. I like how Twilight continues her leader role by calming everyone and bringing them together. I don't know if anyone made this metaphor, but she's the glue that keeps friendships together, ironic given that initially she wasn't interested in friends at all. I also liked Twilight's explanation for why she wasn't scared; having read the princess sisters' journal, she knew all about the castle and thus it wasn't that scary to her. The fact that she's easily distracted by books also helps.
One last thing I kind of liked was that the letters thing was replaced by a journal, which Twilight suggests after reading Celestia and Luna's journal. Some people might be surprised by the replacement of the letters, but then again, it makes sense, seeing as the letters thing was an assignment from Celestia to Twilight as her student, but now that she's ascended to princesshood, she doesn't need the letters anymore (though I'm sure they'll keep them just in case), so now we can still have lessons/summaries at the end of an episode, just through the journal... I don't see why, since I figure by this point they'd just abandon the whole concept entirely, but it's still a nice sentiment and I look forward to the entries.
Now for stuff I didn't really care for. Like I said, the whole episode feels really cliche, stuff you'd see in any given "group goes into creepy place, finds out it was just their imagination the whole time" storyline that... I feel like I've seen a lot of. Lines about ghosts, and AJ and RD being scared, I feel like they're almost "cringe-worthy", though thankfully, they never get too painful that I stopped liking the episode. Before it all ended, I "knew" that Pinkie Pie was the one playing the organ and that there would be a logical explanation for everything. Speaking of which, while I liked Pinkie's rambling at the beginning, here it's a lot more annoying, especially when she assumes that everyone getting scared in the castle was some sort of party, and went "duh!", like seriously, THAT gets on my nerves so much. Hey Pinkie, not everything you think is obvious is obvious to everyone, especially since you're a cuckoo-brain! I liked the "imagination leads to cake" line, though. Also, I think the most annoying aspect of this episode was the most cliche thing out of all the cliched things in this episode, when everyone says "I guess there was nothing weird about this place after all!" then all of a sudden "OH NO, THERE WAS A WEIRD THING THE WHOLE TIME!", I don't even need to list examples, I've seen this so many times it feels ridiculous to see it here! What's irksome about it, for me anyway, is that it's one of this last-minute teases that they're never going to touch back on. I mean, why should they? why should they revisit the "Pony of Shadows" thing after the mane 6 already concluded that it was all in their minds? It's just really annoying and pointless to me.
Now for some nitpicky things. Why did Rarity restore the tapestries when she was just going to return them? I guess because of what happened, but really, they proved that there's nothing supernatural about the place, so why not take it home, use it for inspiration, then put it back? Twilight's line about Spike's sarcasm really annoyed me, and I don't know why. I find it incredibly strange that she ignored the organ-playing and all the other noises, yet decided to check things out when she heard ponies screaming. What was so strange about the hall of pony legs? I mean, they're clearly statues, right? Sure it's a weird design choice, but I don't find it all that spooky. Why are there so many trap doors and secret passages in the castle? Are there just as many trap doors and secret passages in Canterlot Castle? Fluttershy crying Angel sounded a little off; I never did get the whole "Fluttershy shouting" joke, because clearly she can scream really loud, so why is she restraining herself a lot of the time? But then again, I love Fluttershy, so I don't care that much.
Lastly, Twilight's home situation. Twilight's in her library, but it's not explicitly stated that she's living there, and seems to be implying that she's looking through the books in the library to see if there's anything about that chest (love the continuity nod, BTW), and implies that she's going back to Canterlot after she's done, mostly to check their library for any information. I kind of assumed this episode would set up that Twilight would live in the old castle, but I guess that was just wishful thinking and letting my hopes get the better of me; after all, the castle is clearly falling apart, hard to live in a place like that. Meghan McCarthy said via a Tweet that Twilight will still live in Ponyville, and I'd like to know how. If it turns out that Twilight still lives in her library, then... well, I'll be quite disappointed, frankly. I figured that being a princess would entail big changes, and not just from a "how ponies react to her" kind of way. I ASSUMED this meant she was going to live in a castle or with Celestia and Luna, because, you know, she's a princess, she shouldn't still be living like a commoner. Having her move would show, from a setting standpoint, that yeah, thing shave definitely changed, and this'll help Twilight learn to deal with these changes while still being friends with the rest of the mane 6. But, who knows, maybe they'll explain where and how Twilight will live from now on, and I'll find it agreeable, but for now, consider me on the fence about the whole thing... leaning more towards the unsatisfied side.