When the Borg launch an attack on Earth, the Enterprise is sent to the neutral zone due to the Admiralty's mistrust of Picard's abilities as he had been assimilated in the past. The Enterprise however, disobeys and returns to help destroy the Borg ship. However a smaller ship escapes and travels back in time, causing the assimilation of Earth in the future. The Enterprise follow the ship back in time and have to undo the damage the ship did on the surface to an experimental warp drive unit that will led Earth to it's first contact with alien life. Meanwhile, on the Enterprise, survivors of the Borg ship begin to assimilate decks within the ship itself.
The trend of the `even good, odd bad' continues in Star Trek with this good entry in the series. Linking to previous story lines, the film starts immediately and continues at a good pace. Where the previous time travel excursion for the crew was more funny than anything else, this film goes down a more dramatic route with the main plot not turning out to be on the ground (as I first thought it would be) but on the ship where the crew struggle to contain the Borg's advances. This aspect works well - it is not edge of the seat stuff, but it is dramatic and involving.
In contrast the stuff on the surface is more a side issue that is used well to contrast with the pace on the Enterprise itself. There aren't many laughs but it does have a nice little bit of self mocking humour that raises it's head occasionally. The cast (crew?) all do good work, but it is Stewart's film and his Borg past help to enrich his character well. Frakes does an able enough job as director but as an actor he has little to do, as indeed do most of those on the Earth aside from a cameo from Cromwell who adds humour. Woodard is OK in her role but not as good as I've seen her be in other things.
Overall this is a solid Star Trek film, which although not excelling in any one area, has a strong backbone of drama and action aboard the ship that works well with the lighter stuff on the earth.