I enjoyed it.
The villian wasn't that great in terms of being characterized like Discord or Chrysalis, but if you just look at it like a environmental evil then it isn't too bad. Plus his horn wasn't destroyed so that may be coming back somehow (maybe Trixie will find it).
Was great to see Spike have an important role. Also worth noting Spikes and Twilights worst fears are very similar, being disowned by the person they look up to.
Looks like Princess Cadence may be the princess of the Crystal Empire, which is a good thing as that would have justification for adding another alicorn into the show last season. Still have many unanswered questions as to whether she was around 1000 years ago, and why she left after they saved the empire.
Also looks like they are finally going to have a plot spanning more than 2 episodes as shown by Luna's book, and the fact that Twilight has another stage of lessons or something to go through.