Over the part 10 years, I have not strayed away from the typical old dacron line for mainsheets and jibsheets. For downhauls and outhauls I switch to kevlar lines a few years ago.

Does anyone have any information on higher performance main/jib sheets? What do you like and dislike about some of the newer materials (Yale Light, Sampson WarpSpeed...etc). I know a lot of sailors that have switched to 3/8" Yale on their mailsheets. I have heard good and bad.

You might find something useful in this thread from last spring:

Sheets -- What Line to Get?

In my research I found it very interesting that the operating weight is so high on some of the new composite ropes.
I think I am going to switch to 1/4" on my jib. I planned on going to 3/8" on the main. I don't know why more sailors don't use 1/4" jib lines.

That last disscussion looked like Yale / Spectra cordage talk. I have already had opinons on it. Anyone try Sampson WarpSpeed?

I use warpspeed on my downhaul, outhaul and rotation arm line. Its very stiff, doesn't handle well, and doesn't run through blocks very well, so I use it for lines that don't do much moving. In fact, I think I'm about to go back to generic west-marine-brand yale for my downhaul.