I noticed this recently, but had an opportunity to try it when I went out to lunch today: Diet Coke Plus, which is Diet Coke with added vitamins and minerals.
Short take is that it tastes fine, although there may be a slightly different taste--I'm not sure if I'm imagining it or not. I actually think the added vitamins and minerals are pretty silly, and I prefer Zero anyway (which is almost as good as the real thing), but there's nothing wrong with it, even if it does sound kind of funny.
And in a related topic, why is it that you always see health nuts going crazy trying to find some way to hate diet soda? There's no calories, it's not really much different than drinking water, except it tastes good. Actually, I suspect that's the objection: If you're not suffering, you must be doing something wrong.
Postscript: The end is in sight. If I finish grading one more final, I can be done with grades for the semester. Yea!