Well, I don't know much about where it comes from, or any elixir of youth properties, but I have tried it.
I ordered some from Tea Spring a few months ago, my interest piqued by the "King of Yellow Teas" name they gave it. I was impressed by the fragrance -- Tea Spring teas are always fresh, but the scent of this one was POWERFUL when I opened the package, even in comparison to the rest of what I ordered. I don't know how to describe flavor . . . it's VERY yellow. Overall I quite enjoyed it, though I think I waited too long and should have brewed it right when it was fresh; when I finally got around to it a week or so later, it had already lost a lot of fragrance.
Worth a premium? I don't know. I like yellow and white teas a lot, and I'm pretty happy with my Bai Hao Yin Zhen and my Huo Shan Huang Ya; those are what I still drink frequently. The Jun Shan Yin Zhen was really yummy and powerful, and I thought it was a neat experience to have once. I might buy it again, but Teaspring only sells it in 'novelty can' and 'drink daily and you might finish it before it goes stale' sizes. It's a very special and unique tea, but definitely doesn't make the daily drinker budget cut for me!