Hmmm, I tried making my own, using a dollop of marmite in a near-empty jar of PB and it didn't go well. It completely dried out so became more of a crumble consistency than a spread.
FWIW I bought some for my brother-in-law who, like you (and me), loves both elements and he's all over it...
Yes, it's delicious – IMO, like*. One of the greatest things I've ever tasted. I love the two spreads separately and bringing them together really works for me. Had a lovely bagel smothered in the stuff this morning.
*It's CLEARLY an acquired taste, so there will be people on here (and...