I found the episode to merely be OK, particularly because it felt rather drawn out and padded. It probably would have had a lot more impact as a 12-minute episode without losing too much. The song was nice, but it felt really unnecessary, as nothing was really changed or made more clear between the start and end... a lot like "Winter Wrap Up" actually. I like how Dash straightforwardly followed the five stages of grief (denial, anger, bargaining, depression, acceptance). The look inside the weather factory was neat, though a bit less was done than I would have liked, and it was odd that Dash apparently got away with messing things up. I liked Fluttershy being cruel to be kind, though given how calm she was, I'm guessing she has had to break the news about pet deaths in the past. I also liked Fluttershy breaking, and thus most everyone else breaking. It was kind of surprising to see Twilight still being presented as somewhat of an outsider in this case.
Also, I guess we now have undeniable proof that the episodes are not necessarily in chronological order. At the very least, "Hearth's Warming Eve" definitely took place before "May the Best Pet Win", and less than a year has passed between the latter episode and now. Just another headache for those bothering to figure this out.
Larson had previously tweeted that he accepts full responsibility for something that happens in this episode, which I guessed would be the use of the quote, "Winter is coming," and I was proven right.