Well, I just finished the episode, and qute rankly, I thought it was really good.
Being a Rarity-central episode more than made up for the last of Rarity last episode. The idea of having an episode dedicaed to the many sibling relationships in the series was a good idea, methinks. For me, this story seemed pretty strong, with some good drama and nice sequences. And that moment of Rarity's realisation about Sweetie Belle...Probably the most heartwarming thing I've seen this season.
As for the humour, this was probably one of the funniest episodes so far. Rarity's parents were brilliant (I wouldn't exactly call them Appleoosan, just excessivly American tourist-y) the ending of the sequence with the sheep definitely got a grin out of me, and Granny Smith had me rolling on the floor.
As usual, the animation was lovely, the voice acting was top notch, and the music was great (I especially liked the music playing during the race. It just worked)
As for the background ponies, I am glad that, even though we now know that Dinky and Seafoam are apparently sisters, and Berry Punch and Carrot Top both have little sisters, they've still managed to not mess with determined fanon relationships.
IMO, perhaps the best non-Discord episode this season so far.