My g/f at times wants butt sex more than regular. We will always start with vaginal sex and then finish with butts sex if that is what she is wanting to do at that time. Like Kronkette said, the orgasm is much more intense there. There is a learning process that needs to be followed as far as moving slowly and not just plunging in. Use plenty of lube and start with something small like your finger for first time penetration and use plenty of lube. Ask often if she is doing okay and use plenty of lube. Once the anus has been stretched sufficently to allow penetration, MOVE SLOWLY and USE PLENTY OF LUBE! Ladies, don't knock it if you haven't tried it!