Even if you grow up with Marmite like I did, you either like it or you don't. If you don't care for salty food this is not for you. Marmite has a yeasty, beer-like flavour and a slightly bitter aftertaste, but is a salty flavour explosion in your mouth. If you have a big mouthful it's seriously overwhelming, but spread on toast with cheese it becomes something delicious and thoroughly yummy.
I have not been able to convert my American husband yet, although I do have him eating salty black liquorice, so we'll get there eventually. I took a jar of Marmite, some crackers and cheese to work with me and had anybody brave enough taste some. All of my colleagues (Texans, the lot) liked it except for one lady who made a face. She has no tact, so for all I know all the rest secretly hated it but was being polite.
If you end up with a jar of Marmite and find yourself to not be a big fan of Marmite on bread, try adding some to soup broth. It's vegetarian friendly, and a nice way to introduce a new flavour to your veggie only fare.
I can not sing the praises of this delicious black goop enough - to be fair though, if it came to a choice between Marmite and Bovril, I'd go for Bovril every time.