Speaking of Discord; I've heard that someponies are not pleased that discord wasn't evil enough. First of all, Discord was never shown to be very evil in the original 2 episodes. He was just creating chaos. If he were evil, he would have just destroyed the ponies with a click of his claws. He wanted to disable their Elements hence the corruption and it was also done for his amusement.
Also, the biggest aspect of the episode is the fact that Discord was able to accomplish 2 very important things:
1. Make Fluttershy swear to never use her element against him
2. Destroyed all of Twilight's books that hold the spells that can banish him.
While he does promise to somewhat behave to Fluttershy and Celestia, the fact is he has officially made it impossible for the others to ever banish him again unless the others can convince Fluttershy to break her promise which could be something rather difficult. However, the most important thing is this:
He does not want to lose his friendship with Fluttershy and yet he is not pleased with having to "behave." If one thinks of it, all he needs to do is "behave" until Fluttershy passes away from old age and then he is free to cause as much chaos as he wants as he is immortal.
Hence Discord's episode had him showing a lot more thought in the future than some ponies may think......
On another note: I am going to be posting the next Rarity chapters soon. I have the next chapter 75% done. Thanks for the patience.