I don't yet own this film on video, and haven't seen it in about six months. As such this review is written entirely from a fairly distant memory. So while I'm fairly certain about the whats and whys, I can't be all that certain about the order things happened in. Please forgive any errors.
The film opens with views of life in an idyllic mountain village - children play, happy looking farmers tend the fields, women chat as they make the bread, etc. However, as the titles end things become more sinister. Shadowy figures are watching the village from within a nearby facility, and we become aware that suited figures are wandering the village, invisible to those living there. Things go from sinister to outright dangerous as we hear phaser fire approaching the village. A suited figure is on the rampage, knocking its fellows aside as it advances on the facility. The marauder turns out to be Data, who is injured and apparently out of control. As the shocked natives, who we will learn are called the Baku, look on he fights off several attacks by the other suited figures before firing his phaser on a nearby rock formation, revealing it to be a hologram hiding the control facility.
Meanwhile, on the Enterprise Picard is preparing for a meeting with some local diplomats. As his officers fuss over him he complains about how they never get to do any exploration any more, but cheers when Worf appears, on a visit from Deep Space Nine. The meeting goes well, but is interrupted when Picard is called by Admiral Dougherty. The Admiral tells him that Data has gone crazy and is holding a Federation / Son'a research team hostage on a planet in the Briar Patch. The Enterprise speeds to join Dougherty, despite not being equipped to operate within the Patch.
As the Enterprise is on its way we are introduced to the Son'a. They are Federation allies, but it is an alliance borne out of need rather than friendship. The Son'a are not Nice People - they have enslaved other species, and are said to use banned subspace weapons on their ships. The Son'a themselves are rather hideous, apparently afflicted with some form of disfiguring disease - or possibly advanced age, it's never made clear - which requires regular sessions of face stretching. As Dougherty talks to their leader, Ru'afo, their ship comes under attack. It is Data again, using a scoutship assigned to the project to study the Baku. He inflicts minor damage on the Son'a ship before heading off again.
As Picard arrives, Dougherty demands that Data be destroyed. Picard prefers to capture the android, but agrees to destroy him if necessary. He sets out with Worf on a shuttle, and they are soon under attack. Picard manages to distract Data by singing a song from HMS Pinafore, allowing him to dock with Data's scout ship so that Worf can immobilize him. Back on the ship Geordi determines that Data's malfunction was caused by a phaser hit, and that in his damaged state his ethical subroutines would have taken over - so his actions were what he considered to be right. Data can shed little light on the mystery - he has no memory beyond exploring the hills near the village.
Picard beams down to the Baku village with an away team and is surprised to find that they are not in fact holding the project members hostage. The Baku prove to be a peaceful people who are knowledgeable of technology but deliberately shun it. He apologizes and beams back to the ship with the 'captives'. Once on board the Son'a refuse to undergo routine medical exams, so Picard isolates them from the ships crew. Dougherty insists that they be returned to Ru'afos ship, and orders Picard to leave the area. Instead Picard takes Data down to the surface and, along with a couple of the Baku, heads out into the hills to find out what happened to Data. They discover a cloaked spacecraft sitting at the bottom of a large lake, which turns out to have a holographic recreation of the Baku village inside. Picard realizes that Dougherty and the Son'a are planning to remove the entire Baku population and put them on another planet without their knowledge. Meanwhile, Son'a reinforcements arrive in the form of two battleships and a much larger vessel.
At first the motive is unclear, but Picard realizes that The Enterprise crew are being rejuvenated by something in the area. The Baku woman Anji confirms that the locals are centuries old but metaphasic radiation in the planets rings prevent them from ageing. Picard meets Geordi on the surface and is amazed to discover that the engineers eyes have regrown under the influence of the rings. Returning to the ship, Picard confronts Dougherty and the Admiral admits that the Son'a have developed a method of harvesting metaphasic particles from the rings, but that the process will destroy all life on the planet. He claims that the Federation Council is in on the scheme, even though it violates the fundamental principles of the Federation.
That night Picard loads the Captains yacht with weapons and supplies, planning to take them down to the surface. Worf, Crusher, Troi and Data insist on going with him, but Picard orders Geordi and Riker to leave the disruptive effect of the Briar Patch and make the conspiracy known to the general public. Ru'afo convinces Dougherty to send the two Son'a battleships after the Enterprise while they proceed to evacuate the Baku by force, since Picard has erected transporter inhibitors around the village. Dougherty agrees to the pursuit of the Enterprise, but they decide to use drones firing isolinear tags to let them transport the Baku up through Picards interference.
Picard evacuates the village as the drones begin to pick the Baku off one by one, heading for the hills where mineral deposits will prevent any more beam-ups. Meanwhile the Enterprise is caught by the Son'a ships and a battle ensues in which the Starship suffers considerable damage. When the Son'a use subspace weapons, Geordi is forced to eject the ships warp core and detonate it to seal a 'tear' in space. Riker turns to fight, scooping up a huge cloud of metreon gas and dumping it in front of the enemy ships. When they fire the cloud detonates, destroying one ship and badly damaging the other.
On the surface the Baku head through some caves to hide from the drones. Although Picard and Anji are trapped by a rockfall, they are quickly dug out and the band reach the other side of the caves and the last leg of their trip into the mountains. Some Son'a attempt to stop them, but Worf uses a shoulder mounted weapon to defeat them. When scanning the bodies, Crusher learns a startling fact... unfortunately, the drones quickly catch them and both Picard and Anji are captured by the Son'a.
On the Son'a ship, Picard informs Dougherty of what Crusher learned on the surface - the Baku and the Son'a are the same race. The Federation has let itself become involved in a blood feud. Shaken by the news, Picard tells Ru'afo that their plan is coming apart and they will have to come clean. Ru'afo refuses, and a fight ensues in which Dougherty is killed.
Picard manages to convince one of Ru'afos henchmen to give up the vendetta, and they come up with a plan. Data uses the Captains yacht to attack Ru'afos ship, but he shrugs it off and initiates the metaphasic collector. The device works perfectly, but Ru'afo soon suspects that something is wrong - and realizes that during Data's attack Picard beamed him and his senior officers to a recreation of his bridge on board the holoship. Picard attempts to disable the collector, but it is impossible to do from the ship. He beams over to the collector to destroy it, leaving Worf in command.
Ru'afo manages to beam himself over to the collector from the holoship, and fights with Picard. As the remaining Son'a crew on his own ship break onto the bridge and overpower Worf, Picard triggers the self destruct and the collector begins to explode. The Enterprise swoops in at the very last second and beams Picard aboard, leaving Ru'afo to die in the blast. Riker then blasts Ru'afos ship, knocking out the life support systems and forcing them to surrender. With the conspiracy shattered, Picard returns the Baku to the surface and says his goodbyes before heading off into space once more.
The basic plot paints a fairly simple picture of ethnic cleansing - you could substitute anybody from the American Indians to the Bosnians to the East Timorese for the Baku, which at least makes it eternally topical! But there are a few elements of the morality that don't make a lot of sense - Dougherty claims that the Federation controls the planet but the Baku don't even seem aware of the Federation, let alone being a member world. Surely this would make the whole thing illegal, so how can the Federation Council have authorized it? Unless there is an arms-for-hostages style conspiracy going on amongst at least part of the Council, with Dougherty as an Ollie North figure. But there is limited exploration of this one way or the other.
The films attempts to portray the Baku as "noble savages" is also a little heavy-handed. The locals claim that "when you design a machine to do the work of a man, you take something away from the man". All the Baku are shown as simple village people living their simple village life, while the Son'a are the opposite - ever more dependant on technology while their bodies and spirits rot away. This is all, of course, blatant nonsense. The Baku claim to shun technology, but the village fields are irrigated, with the local lake apparently an artificial one complete with a dam. Doesn't this "take away" from the people who would otherwise presumably have to walk great distances to bring back water? For that matter, doesn't the very idea of farming take something away from the hunter-gatherers who have been replaced by this technology?
However, such nits don't really make all that much of an impact on the film because ultimately this is more a comedy than anything else. Most of the humour centres around the effects of the crews rejuvenation - Worf regresses to puberty, getting a huge pimple on his face and raging hormones. Riker shaves his beard and he and Troi start acting like a couple of teenagers, while Picard gets his youthful hearing back and starts dancing in his quarters. On this level the film is fairly successful - Data is the straight guy for most of it, and his reactions to Rikers clean shaven appearance and Beverly and Troi's discussion of their rejuvenating breasts is hilarious. On the first run-through I did begin to get a sense that this was all not quite right, that these people really don't act this way. But once you know that the planets rings are causing these kinds of effects it gets a lot easier to accept - as a result I enjoyed this film a lot more on the second viewing, and overall I liked it enough that I saw it at the cinema six times, more than any other Trek film.
The actions scenes are both better and worse than those in First Contact. On the one hand First Contact was an action film, so the relative brevity of the battle sequences was a bit of a let down. In Insurrection the space battle scenes are also fairly brief, but it's not such a big deal since this just isn't that kind of film. So much for quantity then, what about quality? Once again the E-E doesn't really get to strut her stuff - we see the ship fire only two photons and a couple of phaser shots throughout the entire film, which makes some sense given that the Enterprise wasn't supposed to be destroying the ships, but rather escaping from them. The effects are quite impressive, what with the subspace weapon, the warp core detonation, and the Metreon cloud explosion. The self destruct of the Collector is also very nicely done. The surface fighting consists mostly of the crew taking pot-shots at drones while the Baku get picked off - no orbital bombardment or anything, which is again fairly reasonable since both sides are trying to do this operation with zero casualties.
Overall then, there's nothing really seriously wrong with this film and there are quite a few moments which are well done or better. It's not a classic, but I don't think it's the total stinker that some claim either.