I remember buying marmite when I first went vegan, so somewhere around 2005. I was somehow led to believe it was similar in taste to nutritional yeast. I made the mistake of trying it on toast and it did not appeal to me. It kind of reminded me of the better than bouillon in a jar. I would never think to have that on toast. And it's nothing like nutritional yeast! I definitely can see it used in savory dishes to add flavor though.
It's difficult to describe the taste and this is what I've found : 'Marmite has a very distinctive flavor. The taste is so unique as to defy description, but think of a yeasty, salty, soy sauce-esque flavor with the consistency of old engine oil. Some people really like eating it, and some people don't like eating it at all.''
Marmite: Americans wonder what's all the fuss over divisive British spread?
Marmite, the ‘love it or hate it’ paste made from yeast extract with a yeasty, salty, soy sauce flavor, was the center of a spat that threatened its very existence
www.theguardian.com
It's very salty and has a deep flavour to it. Not for people who like very sweet spreads on toast.