It slows down the beginning a bit, but at least it doesn't take up too much time, and is ultimately beneficial for the audience. There are a few annoying moments where they add in some flashbacks from early episodes of the show so that people who haven't seen the show knows what's going on. Overall, the plot is fairly straightforward with some twists and turns. It fits in with the show, while remaining a self-contained story. That being said, this movie is a high-budget arc of the show.
I don't think that its as great as everyone says it is, its a bit cheesy and stupid at times, but overall its well written and animated.
