This movie is vulgar, often stupid, and hilarious. Their live action Scooby Doo gang beats the movie cast and is almost worth a rental all on it's own and where else will you get jokes so vulgar that they earned an NC-17 before a few were cut AND a cameo appearance by God Herself?
The sequence where they manage to simultaneously make fun of Batman and Star Wars with Mark Hamill as the villain is the highlight of the movie.
This movie has more pop culture references than any other I can think of but unfortunately this includes many references to Smith's previous movies. I think to really follow what there is of the plot you have to have at least seen Chasing Amy and Clerks but you're going to miss something if you haven't seen all of the prior films. The ending bit won't make sense if you haven't seen Dogma but might still be fun on it's own.
NOT for kids even though 13-year-old boys would love it.
Buy this movie, it's cheaper than Prozac and has more pleasant side effects.