Fortunately I have not experienced circular saw kickback or chain
saw. I have read about it and I am wondering how strong it is,
though. I know the answer probably depends on the HP of the saw, the
material being cut, user posture and strength, etc. Is the force
imparted so strong that a reasonably healthy guy would still be able
to hold onto the saw (with two hands) or does the saw simply go flying
out of your hands?

Thanks,
Tim