This is a wonderful episode, and have to say my favorite of all the season. I loved how the CMC sound when they sing together, and the song "Light of your Cutie Mark" was AMAZING!!!
I also enjoyed how Diamond Tiara flipped from being mean to being good in this episode. I never really liked her in the older seasons because of her being mean to the CMC, but now in this episode. It made me respect her more.
Overall this is my favorite episode ever from all the seasons.