On first watch, I would have given this one a "B," but upon second watching, I'm bumping it up to an "A." Another great episode!
I liked who many of the characters had lots to do and good comedy. Pinkie was the comedy highlight for me, with the hilarious "Nooo!/Yessss!" dramatic running gag, her acting completely goofy to distract the "not"-inspector, and her squee after offering Cadence a cinnamon bun. Rarity was in great form first for her love the spa, then for her pushing Twilight away when trying to fix the headdress. It was cool to see Rainbow's father in the flashback, and her falling into the dome while Rarity thinks she hears something was really funny (I also got a kick out her saying "and, we're walkin'). Twilight being (mostly) calm was keeping in recent character development, and cute to boot. And, while AJ and Fluttershy didn't have too much to do, they were perfectly in character.
The guest pony was unique in that she got such a large focus. She was a nice, appealing character that was well-acted and had some unique quirks (for this show, at least) like being claustrophobic and nearly outrunning RD on land when getting free. I also got a kick out her flirting with Shining Armor--something you don't see much on this show often either. (The chase scene also had some great music from Will Anderson to boot.)
The linking with "Sidekicks" was fun at the beginning and the end.
A solid "A" right up there with "Crystal Empire, "Too Many Pinkie Pies" and "Magic Duel" for my favorites of the season. Now, I'm looking forward to the season finale!