Ok, despite similarities to Lesson Zero (one of my "meh" episodes), I surprisingly loved this episode. Personally I didn't find it nearly as predictable as everyone else, even though I'd been spoilered enough to know what was coming. Pinkie was good in this episode too, but I wish Twilight had chosen a different pony to come along with her, Pinkie gets enough screentime as it is.
Also, there were like 4 or 5 lines that were almost a
direct quote from Homestuck, a series that includes a huge amount of time travel. I think this might not be a coincidence...
Oh, and I remember a bunch of people thought it was weird how serious Twi got when she traveled back to the past. Thing is, she'd already seen that happen, so if she didn't do it the same way, it would have caused a Paradox. She didn't really have a choice! Not that she was thinking clearly anyway.
I liked the Unicorn guards, how they had flashlight and unlocking spells. Those guys are kind of cool.