I started drinking it with butter before it became "a thing." I just stir a little pad - maybe 1/2 - 1 teaspoon - right after I pour it into the mug.
I originally did it because I thought it may cut the acidity - I use salted butter and a little salt in your coffee really works!
It also, quite literally. makes the coffee smoother.
I think the official "bulletproof" version is made differently, so don't go with my simplistic approach.
As for benefits and is it meant to replace a meal? Excellent question. Definitely not my version but if the real Bulletproof version somehow includes the nutrients you need, than perhaps so.
Glad you started this thread - now I'm interested too