One thing to remember is that guys are often fed lines when growing up and get the wrong ideas from movies (chick flicks). Women are all about the emotional side of sex, women like it slow and tender, women blah blah. When the whole time the dude is thinking "Damn, this is boring. I wish I was back in high school just destroying this sh*t" and the woman is sitting there thinking the exact same thing. Communicate folks.
edit - cross posted with Magnolia who is right as she usually is. damn it.