What I really miss is Surge. Surge was marketed for a couple of years, but not nationwide--it was not available in the south suburbs of Chicago, for example--and Coke withdrew it after it failed to beat Mountain Dew into a small brown stain. (Well, if they had tried selling it everywhere it might have done better....)
Surge had a better flavor than Mountain Dew and it was antifreeze green. It didn't flouresce like antifreeze but it had the same color--it's the ethylene glycol that makes antifreeze flourescent--and it was tasty, tasty stuff. I was a lifelong Pepsi drinker until Surge came around; that's how good it was.
And then it went away.
7-up released dnL in 2003 ("dnL" is "7up" upside down) and it was green and caffienated, and it tasted like Surge. But dnL went away, too; and now we have Vault.
Vault is Surge, with a different blend of artificial colors. I'm pretty sure of this. Coke is marketing it as an "energy drink" but it isn't; it sure as hell doesn't taste like one. The stuff they put in "energy drinks" make it extra-bitter--the taurine, ginseng, caffiene, etc, etc, which requires them to load up on sugar to sweeten it, and the end result is a flavor which makes me think of vaguely sweet battery acid, and has about the same effect on my stomach.
Red Bull has saved my bacon a couple of times, when I really needed a boost; but I do not make a habit out of using energy drinks because the energy you borrow with them has to be repaid, sooner or later. Overusing stimulants (even caffiene) can really screw you up if you make a habit of substituting them for sleep.
But most soda doesn't even have as much caffiene as a typical cup of coffee, and if you're one of those people who drinks double-espresso you're slamming down the caffiene equivalent of four cans (or more) of caffienated soda. Mountain Dew has 55mg of caffiene per can; a typical cup of coffee weighs in around 100mg and espresso is ultra-coffee. (And some folks drink coffee that should pour like maple syrup, it's so thick. I don't know how they keep their hearts from exploding.)
Anyway, Vault tickles my taste buds much the same way Surge did; when I slug back some cold Vault, I get the same reaction I always got when drinking Surge. Mello Yello is not as good, definitely. It's not even as good as Mountain Dew is.
I never used to like Mountain Dew. But Surge came and went, which got me past my Pepsi habit; then a friend of mine--the guy who was my DM out in Iowa--got a soda fountain in his double-wide, and on game days you could chip in $2 for unlimited refills. Unfortunately he didn't like Pepsi (the uncultured lout!) so I had a choice between Coke, root beer, diet Coke, and Mountain Dew.
And the Mountain Dew from that fountain was perfect. So I drank that, because Coke kicks my kidneys into overdrive. So after that I drank Mountain Dew a lot.
But then Coke came out with Vault. Yahoo.
...still, I can tell that Coke's not pushing the stuff very hard. The Target I work at no longer stocks it, and where we do our grocery shopping there are typically about two cases' worth of 12-packs (no full cases) and that's it. When it's on sale it sells out fast there.
Still, one can hope that Vault is here to stay. It's certainly better than any other "citrus soda" that's on the market.