I've been running the Scotty braid (250 lb test) on one downrigger for two years now. Wasn't too sure about it the first year as it seemed to hang back a little farther than cable (it is marginally larger in diameter) but after two years, I like it. I'll be replacing the cable on my other downrigger with the braid. It is a little spendy compared to cable, but much easier to work with.

I haven't seen any problems with fraying. I use the Gold Star snubbers on both downriggers. They are really nice and absorb a large portion of the strain you get when stopping the ball. They also making pulling the ball into the boat much nicer and safer.

One potential problem are the plastic stoppers. The yellow and black ones for cable can slip on the braid. I understand that there are red ones for the braid that hold better. Haven't put those on yet. In the interim, I took a black permanent marker and colored the braid below the stops. I left a few inches for reference and can re-adjust if they start slipping.