60% of the time it works all the time.
I nearly took my leg off twice in one day cutting in brush with no chaps when learning to use a saw on a land clearing job many years ago. It was my fault and lack of experience. I have since learned some respect for my machines and made a few upgrades as well but I never pick up a saw without my chaps on. Definitely cheap insurance and they add an extra later of warmth in the winter as well.