The swearing, occasional graphic violence and sexual references may put many people off this movie.
But the movie doesn't care. :)
The South Park movie is a remarkably amusing tale of the chaos which engulfs a small town when its children sneak into an R-rated movie and (gasp) learn naughty words! (As if the South Park kids didn't know enough already.) Soon the mothers of South Park are up in arms and badgering the President to wage war on Canada. Unknown to them, they are the pawns of a world takeover by Satan and his gay lover, Saddam Hussein.
The film relies on the same shock humor (some of it, frankly, over the top) and contradictions of modern society ("Remember, horrific, mind-numbing violence is okay, as long as there are no dirty words!") as the television show, as the mothers go to the lengths of implanting v-chips in their kids' heads, executing actors, and waging war in order to protect their kids from potty-mouthed movies.
The animation is the usual South Park paper cut-outs...there's even a bit of a side joke in the film about it, when Cartman expresses disinterest in seeing the Terrence and Philip movie because "the animation is all crappy." There are also some cool CGI scenes in Hell, following the usual death of Kenny.
But what lifts this film above being just an extra-long, extra-foulmouthed version of the TV show is the surprising presence of some really fun and well-written songs, often accompanying musical-style dance productions, and mostly parodic in nature. 'Blame Canada,' the showpiece song of the film, has all the mothers melodramatically proclaiming how Canada has corrupted their children with their films. ("Don't blame me for my son Stan, he saw the darn cartoon and now he's off to join the Klan!") "I wanna be up there" is a wistful, dreamy, longing song worthy of any misunderstood Disney hero...except that it's sung by Satan. There is a wonderful scene where Mr. Mackey sings the kids a song--"It's Easy, M'Kay?" urging them not to swear. In fact, there's not a dull song in the film.
If humor in bad taste doesn't appeal to you, avoid this film like the plague. Others will find it good for quite a lot of laughs.
The soundtrack CD is also worth looking into...unfortunately, the movie songs weren't enough to fill the CD, and a lot of other stuff by various artists was added, much of it not worth hearing. (Also, strangely missing is the song 'Little Boy You're Going to Hell' from Kenny's death scene.)