I don't drink the Mtn Dew sodas, but I'm addicted to their Kickstart energy drinks! Mainly because I don't get that jittery over caffeinated feeling as I would from a Red Bull. It just increases my energy and gives me that boost for the day. And I don't crash from them either.
They're most likely horrible to be drinking, but most of the flavors are good, and they work (for the most part) when I need them to.