This is a "curb rating" on my part.  I'd rate it about a 2.  It does deliver on its promise of heat, but the flavor is just nothing to write home about.  If you've ever eaten old, dried cayenne straight from the jar, that's exactly what this tastes like.  It's earthy, bitter, and simply put, lacking complexity.  The onion and garlic and stuff that are supposedly in there, just don't hit home, and the fresh pepper flavors you get with less cheaply made sauces, isn't anywhere within a mile of this bottle.  Furthermore, I can eat about a spoonful of this before I feel the full mouth, in-my-face pain.  It says one drop at a time, which might be true for some people, but if I want to get the real spice going- the brain tingling, endorphin-pumping kind- then I need a few shakes.  It's actually not that much hotter than sri racha sauce, which tastes SO much better, and doesn't rely on added capsacin.  I was on Skype the first time I ate this, with my boyfriend.  He wanted me to do a review while I dealt with the pain (he watches a guy who does reviews of superhot hot sauces, just after trying them).  He asked me how it was.  I sighed, and, without any drama at all, said... "...Hot."  He laughed, and said, "Aww, you sound so sad!"  It wasn't intentional, but the lack of flavor... not heat, but FLAVOR... was just intensely disappointing.  You'd get more flavor out of some finely chopped habenero, and about the same heat.