I've casted the Sharkskin, and while I don't believe its worth $100, the line is pretty amazing. It shoots NOTICEABLY better then any other line I've casted. I tried it on a 9 weight and was throwing full lines with limited effort. One big problem, for me at least, is the sound it makes as you cast or strip it through the guides. It is actually loud.
For the most part, fly lines are fly lines is fly lines. Best advice I can give is to clean your fly line regularly. Youll get an extra season out of it.
As for the 5 weight, distance certainly can be necessary. The 5 weight can be used on the Big D, the Esopus, Willowemoc, and all those other rivers up there. However, I do agree that distance should not be a major concern locally.