Whipping a slave tied to a cross is possibly the epitome of the SM in BDSM. It can be the most intensive form of play for both the Dominatrix and slave and a leather whip can produce a range of sensations from sensuous right up to the extreme. For many subs it can get them into that glorious sub space quicker than anything else. However, like most things, you either love it or hate is and some just never enjoy the sensation.
Fortunately I have a slave that enjoys the whip and makes the most wonderful noises as it falls on his back.