I was actually thinking along the same lines for a new 60m linked dipole and hoping it would be a bit lighter than the old wire one. Looking for lightness rather than non-stretch as i retune it every time it breaks at the centre. Also possibly replacing the old long-wire and counterpoise and going back to using that with an ATU to be more speedy and flexible with band switching. I suppose the Kevlar is about twice the price of ordinary light-weight antenna wire, so not really an issue when the rest of the gear is a bit more costly 
73,
Rod