It might reduce sexual sensitivity, but it obviously doesn't really effect sexual performance or interest. All the men in my family are circumcised (even the ones on the not-Jewish side, I don't really know why), and all the adults have children (and I once walked in on my brother masturbating because he had headphones on and didn't hear me knock on the door oh god ohgodwhyaaaaaaaaaauuuuugh).

So if the guy I marry is also Jewish, I'll probably have it done on any male children I might have. Unless they seem likely to be headed for Antarctica.