The creators of South Park are interviewed with some interesting results. This exchange in particular struck me:

Parker: Didn’t the Mormon Church just issue a thing that’s like, “This show might actually be designed to try to entertain people for an evening, but the Book of Mormon will change your life and bring you closer to Christ”? [Laughs.] Which is funny because that’s actually what we say in the show, too.
Stone: It’s so funny, that’s our statement!
Parker: We should put it out!
Stone: “We agree … ”
Parker: “ … that book might change your life, but this show will entertain you for an evening.”

I don't remember reading the LDS Church's statement, but things like this have never had much impact on the church's growth. Anything that makes people curious may lead them to investigate the church and that does change many lives. When you consider how these guys have treated religion in general, it's probably a sign of the success of the LDS church to have them focus on it.

I wouldn't pay to watch my beliefs lampooned, but I'm not going to lose sleep over it either. It's been going on since the church was founded in 1830.