Oh GAWSH I LOVED IT. Discord was awesome, and I agree that despite being reformed, he isn't ruined. It opens up several plot ideas (at least for me it does) and adds a whole new dimension to his character. I mean, what if he still has that evil side to him and it decides to show itself again? Drama... >:3
It could be better if it was a 2-parts episode. I'm still trying to understand how the hell Discord was reformed so quickly. Not saying Fluttershy isn't best pony able to do something like this, it's just... c'mon, Discord went from "the eternal master of chaos" to a "baby, I'm so lonely" thing in two seconds. (obvious referrence to this: [link])
That just confirm to myself what i was afraid of: I was the whole time overestimating his "badassness".
As many people have said, I felt the pacing was sort of off. I honestly think they could have just cut out the whole scene in the beginning with Applejack and Fluttershy with the beaver. We already know that Fluttershy is good with animals, and it doesn't seem necessary to show that beavers could flood Sweet Apple Acres. That time could have been better spent with character development, I would think.
I'm also hoping that they don't change Discord's character too much. Being random and hilarious is what makes him enjoyable, and he can still be those things without causing harm to others. I'm wondering if he'll be helpful in defeating a big enemy later on (teamed up with the Mane 6, Celestia, Luna AND Cadence would be pretty epic).
Like many, I thought Discord's development into a (potential) ally was rushed and the climax kind of fizzled with me. It would have been nice to see another 2-parter; maybe even with the majority of his powers being sealed away. He went from being a godlike fiend to being a gradeschool bully in the blink of an eye. I am somewhat disappoint. But I was pleased with Fluttershy throughout the episode. She stayed true to her character, even as her friends played the antagonists. Overall: Average. But with a good lesson to learn: To have a friend, you have to be a friend. yay!