The plot felt a bit forced at times. Diamond Tiara and Silverspoon were well-characterized, but the CMC's response to them was a bit lacking at times. With the exception of Sweetiebelle, the trio remained almost entirely passive, never once attempting to take control of the situation, instead just letting things happen. Furthermore, none of the three struck me as a huge attention-seeker before, nor as someone who'd need to be: I always considered them fairly well-established in the social hierarchy at the school.
Oh yeah, and the social hierarchy. Remind me why Diamond Tiara and Silverspoon are so popular again? Take Randall's performance: why did literally ALL the foals (sans CMC) cheer for Diamond Tiara when she didn't do anything? In fact, I'm not sure in what sense Diamond Tiara and Silverspoon are popular to begin with: they don't seem to have any friends beyond each other, and actively attempt to exclude everyone else.
We got another glimpse of their internal dynamic, though: Diamond Tiara is definitely the boss in that relationship, with Silver Spoon being the subservient one. I wonder if Silver Spoon's ever gonna leave Diamond Tiara's side, and if so, what Diamond Tiara will do. (Might make for an interesting episode, and serve as Diamond Tiara's moment of redemption!)
Diamond Tiara and Silver Spoon apparently also didn't know where Twilight lived. That's surprising; I thought it was common knowledge in Ponyville. OTOH, they are fillies, and likely not the most likely to visit a library for that matter.
Twilight herself was well-written, good-natured, friendly, approachable and welcoming; she didn't mind the attention, and never blamed the CMC for making her the center of it, even when it was undeniably their work. She was also rather cute at the Hayburger restaurant: princess or not, she's still not above thoroughly enjoying her food.
Speaking of which, fast food and fast food restaurants are apparently a thing in Equestria; I'm not sure how I feel about that. (Not so much because fast food's bad as much as because it implies industrialized food production on a scale that's at odds with the level of technology etc. we've seen in Equestria so far.) Also, Pinkie's working there? I really hope she didn't quit her job at Sugar Cube Corner.
Something else that's a thing: braided manes and tails. We knew that before, of course (just look at young Granny Smith, for instance); still nice to see, though, as braids are highly adorable.
Random bits: Scootaloo posing for the camera was quite amusing; that kid may have a modelling career ahead of her. (Maybe Rarity/Fluttershy can hook her up with Photo Finish when she's older.) Colt character models continue to be exaggerated/weird, while fillies get normal-looking models instead. Silver Spoon calls Diamond Tiara "Di". Spike just can't catch a break, the poor guy — but at least he and Twily will have enough nachos to last for a week. The CMC's last lines were spot-on, their disguises really were fairly silly (those glasses!). And finally: Twilight has a research poster for the box from the Tree of Harmony. Nice to know that someone's been doing her research all along. :)
Elsewhere: discussion in broniesaremagic. Episode follow-up on EqD.