Even as a huge South park fan, it does not really have that much replay value, but other than that aspect, I thought everything in the game was extremely well done.  If you like the show you will love it.  Basically a 12 hour super vulgar episode, with good RPG gameplay to boot.  The Zelda series nod in the games later portions is EPIC also.

The only actual replay value is using the different classes, but all that really means is seeing the different characters' attacks.  The actual game plays out the same no matter what class you use.

yeah, the vulgar part is why I have stayed away so far.  I'm not really a fan of excessive vulgarity.  Which means the show is pretty hit or miss with me as well... Maybe if it gets cheap I might pick this up, but from your description it probably just dropped off my radar...

The game is noticeably more vulgar than the show, and should not be played anywhere near children.