Honestly, I thought it was ok. I mean come on, ponies turn humans? It's a cool idea, it just needed a few things fixed, really. There were a couple of things that could have been improved though.
The movie had an ok storyline, I just think it could have been paced a little better, and a song or two could have been cut. The characters were great because they didn't alter their original personalities, the only thing that would have been better would be all of the ponies going instead of just Twilight...Wouldn't it have been more interesting if every pony went instead of just one?.
Sunset Shimmer was a good villain, but she could have gotten a bit more of a back story...It just seemed a bit rushed when a sudden character like her was introduced without more of an explanation... I mean it would make more sense if Discord or Chrysalis did it?
Basically the storyline was good, but it wasn't as in-depth as the show. It was predictable and dragged out a bit, however the school setting should have been changed to a town or something. The love interest wasn't bad, but that could have been done differently too.
I know that they were trying to appeal more to younger girls, but they could have portrayed everything so much better.