I didn't understand the purpose of this drink until a couple days ago. I was hesitating to drink another Diet Coke because the caffeine would keep me up late, so I grabbed a Caffeine Free Diet Coke just to try it. It tastes exactly like Diet Coke (at least to me), and that taste itself seems to make me feel more alert, as if I've tricked my brain into thinking it's getting some caffeine. Maybe decaf coffee works the same way? Maybe I'm just dense to not have realized this would happen before. Anyway, kind of cool, although my dependence on caffeine, while not that strong, is a bit frightening.
Incidentally, I've wondered what the deal is with the new Coke C2, which is advertised to have all the taste of regular Coke with half the carbs and calories. If this is true, why would anyone ever buy regular Coke? And while I like the taste of Diet Coke, which has no carbs or calories, isn't this an admission that most people think it tastes worse than regular Coke? A Google search shows that I'm definitely not the first to wonder about this. But, it looks like most people don't think C2 has all the taste anyway.