Although less well-known than later Ghibli films such as Spirited Away, Nausicaa is (in my opinion) just as good as these films, and probably better in some respects.
For those who didn't know, Nausicaa was originally a manga by Miyazaki, which he was persuaded to make into a film. The manga is actually very different to the anime, so is well worth checking out if you enjoyed the film but were put off the books due to fears of buying the same story (which I have done with some "film comics" in the past...)
The first thing that struck me about this film was the quality of the imagery. It was made in 1984, and back then the art hadn't really been developed very far, plus the team was on a tight budget, so what they have managed to do is very impressive, and still stands up to scrutiny today. The opening shots are very effective at setting the tone of the film, with ruined villages offset by lush jungle and sweeping barren plains. The art style is consistent throughout, although occasionally the characters seem a little too cartoony against the more detailed backgrounds.
The story is quite complicated, and I didn't get all of it the first time around. The film is set 1000 years after a global war that destroyed almost all of civilisation. The few remaining humans have survived alongside the Sea of Decay (Poison Jungle in some versions), that covers most of the planet, and is ruled by giant insects called ohmu. The titular Nausicaa is the princess of the Valley of the Wind, a small, peaceful kingdom by the sea. It is the wind blowing from the sea that prevents the jungle's spores coming into their land, and the people lead happy, safe lives alongside the Sea of Decay. However, one day an airship from another kingdom, Torumekia, crashes in the Valley, and (without spoiling the plot), is found to contain something that has been proven to have the power to change the future of the Earth, which the Torumekians plan to use to their own end.
Although you will probably lose track of who's from where (another kingdom called Pejite gets dragged in as well), the plot is thrilling, awe-inspiring and thought-provoking. Be sure to sit through the credits, as they play over some shots depicting the events after the film, and help to bring it to a satisfying, if slightly clichéd, conclusion.
The sound in the film is passable, with the opening theme being the only piece that really stands out. The American dub is alright, but some actors seem awkward in their roles, and the script is (like most dubbed anime) changed quite a bit, although the same general messages come through.
The film is rated PG, but there is quite a bit of senseless killing, and some scenes would be scary for very young children. There is a never-dying rumour that Nausicaa isn't wearing any underwear, and there are a few shots of her bare behind, but she is actually wearing pale-coloured trousers, and the skirt-type garment is just her coat (everyone else is wearing one in later scenes).
Despite this, I would recommend this film to everyone, as it delivers everything you would associate with Miyazaki's other films; beautiful imagery, thought-provoking plot, frantic action and engaging slower scenes. No-one can be called a Miyazaki fan until they've seen this original masterpiece.