I used to use this kind of stuff (I used Agribon 50 rowcover, a similar product). It didn't give much of anything in the way of protection - the figs died back to how high I had piled the leaves around them. I think the major problem with rowcover is the wind just blows right through it. Thats why I switched to using the reflective bubble insulation: get a strong wind barrier. For two years in a row with the reflective bubble wrap I have had zero dieback.
Scott