Given that I was on board with Starlight Glimmer since even the S5 finale, I was really disappointed by how uninteresting I found this episode to be. Starlight's most interesting traits aren't really built upon, Trixie is at her blandest, and Twilight is both unsympathetic and uninteresting. Meanwhile, multiple elements feel rehashed from "The Crystalling." Didn't enjoy any of the attempts at humour, either. Wrote a review on my blog (http://bit.ly/1VZMI57) where I go more into detail about the characterization here. Really disappointed by this after how much potential I saw in the premiere.
Additional thoughts:
For an episode which is ostensibly about Starlight, the bulk of its character development and thematic depth is actually focused on Twilight. The apparent focus on conflict between Twilight and Starlight remains way too tame and predictable to be all that interesting.
Baffling to me that the episode has entire scenes based around Starlight's impulsiveness only to completely fail to address it in any meaningful way. Doesn't help that, aside from the speech spell, most of the impulsive stuff she does is pretty underwhelming. That's the kind of thing I'm talking about when I say that this episode completely failed to make anything of the nuances of these characters. Maybe this kind of setup would be more satisfying if every episode didn't have to be self-contained.
I've been dissatisfied with Twilight's characterization for a long time, and even though a few recent episodes had given me some hope, this could very well be the last straw for me. I enjoy this character because I identify with her; I didn't find her even remotely relatable in this episode, and worse, I didn't even like her at all. Upsets me.
My comparison between Sunset Shimmer and Starlight Glimmer isn't entirely fair, as Starlight is very much not Sunset, but although I do like that Starlight's approach to redemption differs a little, I'm still waiting for something interesting to be made of it.
I think it would be interesting if Twilight's attempts to adjust to the role of a teacher ultimately fail in some horrible way, but I highly doubt the show will go there. Now that she's learned to be hands-off in teaching twice this season, she's gotta actually remember it next time.
I'm not bothered that Starlight is making jokes at all about her misdeeds, but at some point it just gets boring. If she's not gonna move on, and if she's not gonna be proactive about being a better pony, then at least make something interesting out of her guilt and character flaws. There's some irony in her commenting on how she used to be "evil" while still showing impulsiveness and a lack of consideration for others; I want something to actually be done with that.