The episode had the same issues that The Royal Wedding had, lack of time, we did not see King Sombra enough, he did not feel like a real threat, just like a villain thrown in at the last moment to put in some tension, the episode itself was good but it could have been much better. Everything with Twilight's new magic felt really great as well as the worst fear door, seeing how Twilight's biggest fear was not loosing her friends, but rather loosing Celestia's pride in her made me understand how she has priorities, and made her feel much more "human".

They really upped the animation, it's quite something to see the animators improving so much as the seasons go.

Anyway, Lord Donut Steel is the least characterized of all the villains. However, I would say he was probably the most crazy-prepared out of them as well. Take note that all the traps he set up to stop people from getting the Crystal Heart were taking into consideration the ponies in the Crystal Empire. And it worked for a 1,000 years. He didn't take into factor any outside forces from being able to locate the empire, or have a unicorn that's able to perform all sorts of magic to bypass most of the traps. Even moreso, he didn't expect a team of Ponies to work together in thwarting his plans. Even that, Twilight and the gang came rather close to losing. The biggest kicker was giving crystal Crabs to Shining Armor's horn so the answer to the episodes' primary problem (keeping the barrier up) wouldn't be solved by the obvious Deus Ex Machina. A smart move on the writer.

Lord Donut Steel was also probably the only villain that I felt worked best when he said absolutely nothing. He felt like a horror film monster to me, where the more airtime he got the less dangerous he became. And the moment he began talking, it became clearly obvious he was going to lose very soon. His design is also the most ridiculous, hence his fan nickname "Lord Donut Steel" (referencing terrible OC designs).

There are a few other things to think about. Lord Donut Steel was technically the most victorious of all the villains we have seen so far. Even when he lost by losing his physical body, he "won" by cursing his kingdom for a 1,000 years and got to watch everypony suffer in misery in his shadow form. He did get the most brutal defeat/death out of the 4 big villains (getting shattered and broken into pieces is about as close to an actual permanent death as we probably get). At least Nightmare Moon is still possible, Discord is just chilling in Canterlot, and Chrysalis is probably finding another population feed off their love. Lord Donut Steel is most likely gone forever.

As for the rest of the episode itself:

-Luna returns! Although she seemed more cold towards Twilight, as opposed to last time when the two seemed to be getting along.

-I really enjoyed the songs, especially the 1st. Adorkable to the max. This might as well be enough to put Twilight to #1, but at the moment she's competing the #2 spot. Ballad of the Crystal Ponies had awesome chorus singing. The final song I wasn't feeling it, but that was mostly because I got distracted as I got to the ending.

-Pinkie Pie is slowly scaring me with her ever increasing ability to disregard physics, and the subtle meta-joke when she was disguised as Fluttershy (since same voice actor). But her little Sam Fisher schtick was very adorable.

-Rarity, stop trying to overtake Applejack's spot with your ham and squee. I liked how she somehow managed to make a hat out of a few straws.

-Fluttershy, adorable as always. When she has the jousting getup, the diabetes doubled.

-Applejack is such a silly pony with her terrible lies.

-Rainbow Dash was simply... dashing in the joust armor. I did feel though that she seemed overly frieeendly these 2 episodes.

-Twilight was really rocking it with her increasing mastery of magic. It did worried me a bit when she started using dark magic, but thank goodness dark magic =/= evil person. It does raise questions now on if Twilight will start harnessing dark magic in the future if the situation calls for it.

-Was great to see Spike pretty much saved the day.

-For the Crystal Ponies, for some reason I felt that they were immortal or something.. I don't know if they were able to have normal lives for 1,000 years, seeing the idea of depressed amnesiac ponies reproducing seems rather off. So my crazy theory is that these crystal ponies have ridiculously long lifespans. THAT or Sombra somehow used magic to keep them the same age all this time just so he can see them suffer.

-Cadence really jumped up on my list due to seeing her struggling so hard to keep a barrier up for the entire kingdom. Her barrier magic wasn't as efficient as Shining Armor's, seeing she seemed to have stayed awake just to maintain it. In comparison, Shining Armor needed no concentration to keep a barrier going. He just needs to periodically reinforce it. Another way to look at it, Cadence is keeping a fire burning with a gas pump, while Shining Armor keeps a fire burning with a large flammable log, and comes back every now and then to add more logs. Regardless though, she definitely shows great willpower. Then in the end it was heartwarming to see the two of them deciding to rule over the Crystal Empire.

-The lesson that was implied was quite reasonable, seeing it was set up early on Twilight thought she had to be the one to succeed. When it became obvious her pride/stubbornness would doom them all, she allowed Spike to bring the Crystal Heart to Cadence. Celestia, why you so troll?

So overall, while the villain is a rather flat character due to lack of dialogue and screentime, the episode was far from bad. The songs felt really Disney-esque, in a good way. I'd give an 8/10. And yes, two points off came primarily from a letdown of a memorable villain. Very evil? Yes. Memorable? Nowhere near close.