They don't sell Vegemite in America (at least not normally)--so if you do try it, it's probably because someone tricked or dared you. Not exactly ideal circumstances under which to make the acquaintance of an unfamiliar, slightly-hazardous condiment. X/ 

It's also really easy (and fun) to make fun of. Anyway, I haven't had it personally, but I'd be game to try it if I ever had the chance.