Terrific song (and a huge hit when it came out), which I'm sure you know is this (for those of you who don't know this cultural reference, it has the lyrics captioned ):I've always wanted to know what Vegemite tastes like, ever since the 1980s and the band Men at Work talked about a Vegemite sandwich in a song. I know it has brewer's yeast in it and is a good source of B vitamins, but I don't know anyone who has ever eaten it. So what does it taste like? You obviously like it or you wouldn't eat it.
As others have said, Vegemite and Marmite have very similar tastes, which I'd describe as salty and yeasty as well as what others wrote (umami/savoury).