Co-Ed hockey would be a more interesting question than Men VS Women IMO. The entire Swiss women's team plays boys junior hockey, and some of them are actually pretty good. Muller was third on her team in scoring last year if I recall and that's a league that produces an occasional NHL pick.
Goalies like Raty and Szabados playing mens league is a good step, but past junior the size difference usually becomes too much, especially in North America.
I played with girls who could make the boys looks foolish when I was younger, but as soon as the boys started graduating to Major Midget and Junior etc, the girls start to get left behind.