If I can be completely honest, I haven't seen much difference.
Part of the reason why men and women seem so different might be... you know, the whole 'opposites attract' thing. Ignoring the traits that you're not attracted to/mystified by and playing up the traits that do, therefore making the two seem much more 'different' than they really are.
Then again, what I could see happening is there being a rather wide difference between men and women, but it's not even close to the differences that everyone 'know'.
It's more a matter of, if you're looking at the big picture, there's no difference at all, but if you get closer, you see differences, but if you get close enough to see many significant differences, there's too much variance between individuals that these supposed differences could just be considered differences between individuals. It's like, we'd have "A through X" types of behaviors women, but if 5/6ths of the types of behaviors are analogous with types of behaviors with men, and most people only show up to have 3/4ths of the traits... well, that's pretty useless, isn't it?