Bulletproof coffee is good but expensive. Tastes wonderful with kerry gold unsalted butter and is very filling. However, it takes a bit more time to make and if you're training a lot, you may find that drinking BP coffee instead of eating breakfast will result in low energy levels. I also find a smoother bowel movement ensues after a solid breakfast of some sort (usually eggs with grassfed butter and sea salt). Since Dave's coffee beans are low-toxin, it's good on its own without the butter and MCT oil. But honestly, there are a lot of better tasting coffees, albeit presumably higher in toxins.
I eat a 'bulletproof' diet now. It's essentially paleo with an added emphasis on reducing inflammation and exposure to toxins such as molds. (And some wicked smaht supplementation.) For example, Dave Asprey recommends cooking on low heat to avoid changes in the cooking oil's fats which confuse the body and produce an immune response (inflammation). And as for toxins, he recommends everything from de-molding your home to eating only low-toxin foods.
Sorry if I'm repeating what you've already read/heard...
If you're mostly paleo, 'bulletproof' is the logical next step in optimizing health and performance. It's great marketing on dave's part, too. It basically says "eat low carb, high fat, organic/natural foods fed their natural diets" (the paleo part) AND "reduce exposure to toxins and focus on lowering inflammation... aaaand supplement intelligently (the 'bulletproof' part)."
Intermittent fasting is one of the absolute best things you can do for short term health/mental clarity and for life extension. Dave's version of IF basically involves drinking BP Coffee in the morning.
Mercola's/Ori Hoffmekler's version is even more potent: IF for 16 hours, do a peak 8 workout then immediately consume highly bioavailable proteins (grass fed whey). I do this when I take breaks from BJJ.
But on training days, you may have a hard time maintaining optimal energy levels and alertness. That's just been my experience, your mileage may vary.