I think the tree lost the greater part of its strength by generating the Elements, so that it's ability to repress the forest (and the Seeds of Discord) failed gradually over a millennium (or more. Still vague is the period in between the Princess Sisters taking control and when Luna went crazy).

where can I watch the premiere?

Here.

New episode, Castle-Mania has been leaked.

While the premiere stumbled and struggled, this episode is much better.

The Good:

- Rarity. I think Rarity is best pony.

- Most of the characters were at their best here. Fluttershy's reaction to thinking Angel was crushed, Rarity's reactions to the events going on, AJ and Dash with their rivalry, Twilight getting lost in a book, Spike's fear of the noises, Angel shaking his head at Spike after Twilight says no one likes sarcasm... Lots of good stuff here.

- The dark humor. There was some really dark stuff in here, but it was well disguised.

The Bad:

- Pinkie Pie... It's not that she was really bad, it's just that the ending when she was revealed killed the momentum of the episode and brought everything to a grinding halt.

- The moral. You know, the one that wasn't actually related to the episode at all.

- The journal. Guess what we're getting now instead of letters to the princess? Boo. Tied with this is, again, dialogue. But only in the last part, and it wasn't as bad as the premiere

The Everything Else:

- Come back to the shadow pony and make that an actual thing.

- Daring Do is most daring pony.

- Was Pinkie Pie ringing the bell with her head? Ouch...

Overall, this episode was really enjoyable. I think this is the sort of episode that S3 was missing.

I'm sympathetic to the complaint about Mood Killer Pinkie Pie, but come on, you had to know it was coming.  And isn't she more of a mood serial killer by now? 

The Shadow Pony at the end was a nice twist, but if they ever come back to it it'll probably turn out to be Zecora! 

I did see it coming, but I really didn't want it to. That thought alarms me because cupcakes.

Probably. I was just hoping for some Nightmare Moon residue or something. Anything sinister would do nicely. And if it is Zecora... why does she look so sinister all the time? Is she trying to make people avoid her? Or maybe she's actually evil!

Pretty good episode, i'd say. More background information, comedy, and Pinkie's incomprehensible scoring system.

Can someone please explain the appeal that Bronies see? Not trolling. I tried an episode out, didn't seem that great. Maybe it was the episode

The writing, for the most part. The characters are very well-rounded and dynamic even as they simultaneously fit into well-established roles. Their insecurities are just delightful

Thanks for the response, I'll give it another go to see if I can get into it.