Star Trek: Insurrection is the ninth Star Trek movie, and most people consider it one of the worst of the franchise. Not being most people, I personally consider it one of the best, and I'll try to explain why.
I admit the plot is both convoluted and highly imperfect. Let's start with a brief summary. Captain Picard and crew are cruising around on official Federation business when they are called up by Starfleet Vice-Admiral Dougherty, who tells them that Data, having been used for a somewhat hush-hush mission, has gone berserk. Dougherty wants his schematics, and seems to be planning to destroy Data, if other measures to stop him fail. Picard is not about to let this happen, and he rushes to the rogue Data's side to incapacitate him by cunning, which he brilliantly does.
It turns out that the Federation is spying on a tiny peaceful culture called the Ba'ku, which lives on a planet surrounded by rings that exude rejuvenating particles. The Federation, weakened by conflicts with the Dominion and others, needs all the allies it can get, and has struck up an alliance with a rather boorish and not terribly civilized culture called the Son'a. The Federation and the Son'a want to harvest the rejuvenating particles from the Ba'ku planet's rings, which will render the planet uninhabitable. So they've set in motion a crazy scheme to secretly relocate the Ba'ku people to another planet, using a flying holodeck. As Picard and his crew get wind of this plan, they are outraged and set out to thwart the whole thing. Picard tears Vice-Admiral Dougherty a new one about betraying the principles of the Federation, and proceeds to protect the Ba'ku people from the evacuation plans. Dougherty becomes increasingly conscience-stricken, and eventually wants to abort the plan, but the Son'a, led by Ruafo (F. Murray Abraham), do not take no for an answer and pursue the plan to its bitter climax.
As it turns out, however (in a plot twist a bit too typical for Star Trek), the Son'a culture is an exiled off-shoot of the Ba'ku culture, and once the evil Ruafo is disposed of, the two cultures initiate a reunification process.
The plot is not simple. Many of the details that make it almost work are mentioned in brief, almost throwaway lines that are easily missed. And still it doesn't quite work. Why can't all the parties just share the planet? It's a big planet, and the Ba'ku, which are very nice people, number only 600! The other great problem is the idiotic behavior of the Son'a. And the decision on the part of the Federation to be allied with them! This stretches credibility a great deal.
However, despite these shortcomings this is none the less a great movie. Because what makes Star Trek great to me is the utopian element. I adore the idea of a super-evolved civilization which has solved all the basic problems of mankind and can devote itself to science, art, exploration and enjoying life. And the weakness of this movie's plot actually proceeds from the fact that the movie is almost too utopian. The Federation, despite a couple of bad judgments, is fundamentally utopian. Picard and his crew are absolutely heroically utopian. Even the Ba'ku village itself is utopian, too! Steeped in all this utopianism, it is very hard for the movie to come up with a proper conflict, because it is precisely the lack of conflicts that characterize utopianism!
What we get in much of this movie is a relaxed atmosphere where there is ample space and time for the characters to breathe, to enjoy, to develop. In most other Star Trek movies (especially the lastest 2009 version) there's just action all the time, but here we see our main characters truly thrive. There is so much in this movie to just plain enjoy, without worrying too much about high-stakes action all the time. The special effects are good, the acting is superb (Donna Murphy as Anij of the Ba'ku is an unspeakable boon to this movie), there are lots of great comedy moments ("Have you noticed how your boobs have started to firm up? Not that we care about such things in this day and age."), and we see many of the characters evolve. This is quite simply one of the most pleasant movies I have ever seen, and I love it to bits. Although the story isn't always great, the movie is still packed with substance, and rewards those who delve deeply into it with many fascinating details. The pace and structure of the story are impressive, and by the time most of the compact story has been told, there is still a good half hour's action climax at the end, where Picard has shining moment after shining moment. Fantastic, I say.