Angst? What Angst?: Averted. While Twilight for most of the story takes her many deaths in stride, she delivers a scathing rant to Celestia about how horrible dying is when it's suggested that her friends died well, and winds up committing suicide when Luna gets killed. After breaking the loop it's made clear that she's suffered immense psychological trauma from repeatedly dying, the stress of being trapped in a time loop, and seeing her friends die over and over. She ends up experiencing nightmares, flashbacks, becomes terrified of making a bad choice with no way to correct it, pushes her friends away and starts turning into a recluse.
Crazy Awesome: Pinkie's suggestion for what will happen if both copies of the Element of Magic were ever to touch
Hilarious in Hindsight: In December 2013, Eakin posted a blog post concerning an announcement trailer for the film Edge of Tomorrow, starring Tom Cruise, and how it was effectively "Hard Reset: The Movie."
Spike would later say, "Well, that didn't work," in "The Cutie Remark", a time travel story.
The entire time loop; being forced to relive an invasion over and over, dying painfully in the process and repeatedly watching those you care about getting slaughtered.
While it's implied that Twilight's death immediately resets the loop, one can only imagine how terrible it would be for Celestia in the loop where Twilight commits suicide, if the loop doesn't immediately restart. Right after having lost her sister, she leaves for a while only to find out her beloved student has now killed herself.
A Stitch In Time demonstrates that several timelimes, including that particular loop, do not immediately cease to exist just because Twilight dies. Main timeline Twilight has undergone somewhere over a hundred loops, while Queen Twilight Sparkle underwent so many more than that she considers a hundred loops meaningless. Now there's a bit of horror for you: thousands of worlds consumed, irreversibly, by a wall of bright light.
Rescued from the Scrappy Heap: During A Stitch In Time, Azalea was criticised for being a Satellite Love Interest, a flaw that Eakin later acknowledged. The reveal (actually a retcon) of her being a transformed former changeling in You Can Fight Fate did a lot to fix this, as did the increased focus on her in Changing Lives.
Squick: The Reign of Queen Twilight Sparkle is tagged with a warning that gruesome things happen during it, and it's warranted.
The Woobie: Twilight, after the time loop leaves her with severe PTSD. Azalea, after we learn what she went through upon being transformed, and how badly she's been tormented by both her remorse because of her changeling memories and the regrets of the original Azalea.