I have been drinking it for about a year. Use unsalted butter from grass fed cows, surpriingly eas to find. I am also using the brainoctane oil they sell on bulletproof. About 2 tablespoons of butter and 2 tablespoons of oil. You must mix Iit with a blender to emulsify the oils and coffee.
essentially brain fuel your brain thrives on ketones derived from the healthy fats. Ease into it though too much oil at first may give you a bad case of "disaster pants".
it's super popular right now and I know many people who swear by it. It is what I consume for breakfast and I am fine till about 2 or 3pm as far as hunger goes.
the bulletproof executive website has a great podcast if you are into peak performance. They even have some cool bio hacks to increase testosterone and sexual health