Aside from being durable, it gives more power and spin to my game. The cheapest Kevlar string. So sweet!!
I should qualify by saying that I love kevlar in the mains (as did Agassi) for control but also for the way it compress the ball. I used to use Tennex Hi-Kev (no longer made). These are better and surprisingly, cheaper. They bite the ball and the harder you swing the more they bite. They are at their best on volleys. Contol, Spin and they last forever - what more could you ask?>