How bad is it? Incredibly crude, it's not particularly funny.
Should you see it? No. If you're a Tom Green fan, you've seen it (and why are you a Tom Green fan).
This is the most polarizing of films. More than 99% of people will hate this and the others will think it's trailblazing frontiers of comedy. There's a sort of punk/cartoon/John Waters-ish bad taste ethos, but it just doesn't work. Crude, aggressive and dim at turns, this should make for a decent vehicle for physical humor; that it doesn't is the fault of Tom Green, both as actor and director. The plot has Green as a guy living with his parents who wants to be a cartoonist, but spends his time aggravating his family. Anthony Michael Hall, Drew Barrymore, Harland Williams, Julie Hagerty, and Rip Torn are wasted. Marian Coughlan, as a wheelchair-bound nymphomaniac/amateur rocket scientist, comes off well. "Top" moments are Green masturbating farm animals, swinging a newborn by the umbilicus and wearing roadkill. Proceed at your own risk.