I thought it was alright, as good as a kid's movie about magical ponies can get, anyways. So, the story is simple enough. Some big celebration is about to happen in Canterlot, and when things are about to start, Equestria is suddenly invaded by the forces of the "Storm King" led by his right-hand woman, Tempest (who has an actual really stupid food-based pony name). This was my major problem with the movie; the Storm King is so insanely one-dimensional.
He invades Equestria with the intent of capturing all four princesses and harnessing their power to use for his own ends. He gets three of them but of course, Twilight escapes and the movie really kicks off. By the end when Twilight is inevitably caught, he reveals his ultimate goal: to get a spot on the TV Tropes page for card-carrying villain
. He's extremely one-dimensional and has literally no goal other than "I'm going to harness the princess's power and take over the world! Because I'm evil! Muahahaha!". And poor Tempest, she gets the short end of the stick. Her horn broke as a child and she made a deal with the king that if she helped him get the princesses' power, he'd restore her horn. Surprise: He used her and never intended to restore it! Shocker!
The king then turns against Tempest, but Twilight flings him off into the sky. When they fall down, all seems well but the king returns and when he's about to blast Twilight and co., Tempest jumps in and takes the blast
, turning her AND the king (????) into stone. The king falls below and breaks into a million pieces, probably the goriest non-gory MLP death ever, but of course Tempest is saved and the movie ends with a pop song.
This was my other problem; I swear to god anyone in this world can commit mass murder and they'd be forgiven if they repent for what they did and say that they realized how awesome/important friendship is. Discord, Sunset Shimmer, Starlight Glimmer (what the hell are all these guys doing during this ordeal anyways?), and now Tempest? Good lord.
The rest was okay. I found the sea pony (called Hippogriffins for some reason) part was pointless though. They get turned into sea ponies, sing a song, and get booted out by the queen after Twilight tried to steal a magical orb to help Equestria. Other parts include meeting up with delivery slaves, formerly pirates, of the Storm King, yet a single song turns them good again. They also meet a sleezy cat that, again, befriends them with a single song. Wowzers.
All in all, I'd say it's alright. I'd much rather see this than the most recent Equestria Girls movie, that's for sure.