Spoilers for episode 2x01, naturally.
I was a little wary of this episode, not so much because of Faust's departure, but because I'm lukewarm on the season 1 pilot, which has a fairly conventional children's fantasy plot (not quite on the same low level as, say, the Care Bears films, and of course with much more engaging characters, but still, there's a resemblance). So I was a little worried that the season 2 opener, similarly heavy on mythology, would be disappointing.
I was wrong. This was definitely better than "Friendship is Magic, parts 1 & 2". I especially want to commend the visual aspect of the show; it's never looked better, and Discord's introduction is stunning.
Speaking of, Discord is awesome. That's not to say that he is a completely innovative villain - he's a malevolent trickster character, similar to Loki, the Trickster in Supernatural, or Batman's Joker -, but he's certainly very entertaining, and not at all watered down considering what the target audience is. He may even be a little too powerful: Discord getting tired of Fluttershy's steadfastness and brainwashing her made for a good gag, but I'm not sure how I feel about it. How much responsibility for their (bad) decisions do the main characters really shoulder when Discord has this much power over their minds?
The cotton-candy clouds and randomly mutating bunnies suggest that Discord doesn't just love, well, discord, but also randomness and chaos and (malicious) fun. I'm looking forward to seeing how this is dealt with in the next episode, because it's much more interesting than having the villain simply want to take over the world for no reason beyond lust for power. (Also, proponents of the "Celestia is a dictator" theory should like this episode. It's implied she totally is a cruel tyrant, having deprived Equestria of the awesomeness of chocolate milk rain ;)).
The allocation of which pony is assigned which elements has always seemed a little arbitrary to me, and that hasn't changed. How Discord turned Pinkie's light-heartedness into resentment and Rarity's love for diamonds into possessiveness was excellent, as was how he tried to influence Fluttershy (with the above caveat). Applejack's turn seemed less convincing, and Dashie's was quite weak (sure, she abandoned her friends, but for selfless reasons; Cloudsdale was being destroyed, at least as far as she knew).
So, the episode isn't perfect. There was a lot of plot in this episode, which made it seem a little rushed. I could have done without the expository CMC cold open, and the re-introduction of the Main Six also wasn't entirely successful. Did Pinkie's seeming disinterest in saving the world look out-of-character to anyone else? (I may rethink these positions on repeat viewings, and/or once the second episode is aired, which may provide some further context.)
But all in all, a promising start into season 2.
(I originally intended to update the text above and make it a full review of the two-parter. The text got a little too long and general for this page, so I moved it to my wordpress blog. Still, I don't like to delete things, so I figure I may as well leave this up as a first draft; if anyone happens to read this and wants to read the finished version, they can go here.)