I like it because I can control how much caffeine I get depending on when I drink it (e.g., morning, pre-workout, post-workout, afternoon pick-me-up...). This is the first (and only) thing I consume during the morning. I typically do 3 scoops in a shaker with water and lots of ice, which is roughly 150 mg of caffeine. I actually really look forward to this in the mornings...
The best flavors are Grape, Watermelon, Orange and Green Apple. You can get it on Amazon, but I go directly through ON because they routinely have discounts and you can score a free shaker depending on how much you buy.