Back in the 1970's, Star Trek started to draw in fans again. The series was in syndication, so a new generation was discovering the show while old fans were renewed. In the midst of this the show's creator, Gene Rodenberry, proposed a new series: Star Trek: Phase II. The series would be a new five-year mission, and several sets were even built.
However, the folks at Paramount had a different idea: scrap months of work and instead launch Star Trek: The Motion Picture. Some of the characters and story concepts were revised into the new film. However, the film was rushed out the door. Many of the special effects (SFX) were incomplete, and the editing was choppy. Still, it was the first new Trek anyone had seen in years, and still drew in quite the crowd. It also launched the film franchise, and eventually Star Trek: The Next Generation (which wound up re-using many of Phase II's scripts when the writer's strike hit).
In 2001, a remastered version of the film was put out on DVD. It has a 5.1 soundtrack, lots of modern SFX, and some editing changes to take out the worst of the slow parts. Amazon has it for $6.99, so if you're a Star Trek fan, there's no reason not to pick it up.
Not all of the FX were redone. Some of the external shots still use the old FX, which still have specks of dust and such on the film, which is disappointing. The new FX are extremely impressive though, still keeping with the original film but looking 100% better. Some new shots were added, too, which makes for smoother transitions of some scenes.
Suffice to say, any geek should pick this one up without hesitation.