There is a question I had pop into my mind when watching the movie, and it's something that I've ruminated on a bit here.
As Sunset Shimmer is threatening to wreck the portal, she says that the portal will close within an hour on it's own. If we assume she's right, then wasn't it a huge risk to spend any sort of time dancing? Even though Twilight makes it back in time (because the plot demands it mostly), what if she had stayed too long and been forced to stay in the alternate!Canterlot for another 2.5 years? What would things be like if she had spent more time with her human friends, and what would her pony friends anxiously waiting on the other side of the portal think/do? If fanworks haven't explored this yet, I'd like to see it do so.