I took a guided trip in Florida back in October, and the guide had one rod loaded with the sharkskin line. I really liked it. It shoots well and floats high.
Still, I don't know if I'd buy it. $100 for a line is awfully pricey. You can get perfectly adequate lines for a lot less. The Sharkskin is supposed to last longer than regular lines. In that respect, it's kind of like Power Pro or Fireline: the initial cost is high, but it has a longer life and a few other advantages.