Okay, I'm gonna spew out my initial reactions to the episode. Hopefully my thoughts will be more organized later.
-The first two songs fit in much better than I expected. They aren't the best songs in the show, but they're not bad. The last (reprise of Pass/Fail song) felt horribly awkward at first, but got better around the part with Applejack singing... actually, the middle part was the only part I really liked. It's my least favorite from the episode. We need an AJ song.
-Plus points for Cadance and Shining Armor being used again, minus points for a completely dull and nearly nonexistent villain.
-Celestia's presentation, while overdone, was still fun to watch. I wonder if there are any negatives to using dark magic.
-The part with Celestia's/Luna's/Twi's cutie marks in the background was really cheesy, but Twi's "mhmm" made me smile.
-Pinkie's party canon bothered me just as much as when I saw it in the preview. It felt really forced. Plus now we're going to see a bunch of new spider pony memes. Blah.
-They didn't fix the animation error where Twi's horn isn't glowing during part of the Crystal Fair song. Hehe.
-Rarity almost stole the show for me with all of her dramatics. As it stands now, I think I like Rarity and AJ more, Pinkie Pie a bit less, and the others about the same. Poor Pinkie Pie. I really felt that she was just written poorly in this episode. I will say that I did like her spy bit though. The Fluttershy costume gag was fun.
I think this is my least favorite season opener. While it wasn't terrible, it just felt too predictable and dull. I was never really nervous that Twilight would fail. I think this would be solved with more time and actually giving the evil villain whom we are supposed to be afraid of some screen time.