My parents love the stuff- I usually just drink it with breakfast as water tastes like shit w/ morning breath. I've heard studies that suggest too much artificial sweetener can stimulate hunger/sugar cravings, but for most of us that track cals daily this shouldn't be an issue. For the average person though- yeesh. Also, I tend to notice that in my office the people that drink the most diet soda are also the fattest (though I know this has absolutely no global validity- just saying).
Definitely masks the taste of BCAAs though!