I... actually really loved this episode.
Including the about face at the end where Discord basically felt like his small little victory was hollow.
He's a being of chaos, chaos isn't inherently evil.
Also, the way he said "Friendshipismagic" at the end made me laugh. John de Lancie delivered that line perfectly.
Also, to the people who were WANTING him to stay evil to prove the whole "some people just aren't worth it" ... it's a kid's show. What the fuck did you think was going to happen? That would have been an unhappy ending.
Also, in regards to Angel... to be fair, Angel kinda earned a little bit of buttmonkey status. He's kind of an asshole
at least nothing absolutely
terrible happened to him in this episode.
ADDENDUM:
Not to mention, doesn't MLP have kind of a tradition for reforming villains in the first place? I'm talking about the series as a whole, when they actually bother to have villains.