I think there's potentially a lot of value in cross-gender authorships (a man writing female characters and a woman writing male characters) when the author in question isn't just a complete goober about it, and actually puts some thought, research and analysis into it.
For one thing, a male character written by a female author gives me, as a male, some insight as to how women view the male animal. I assume that the opposite would be true, because I can't really test that directly.
For another, I think there's something of a barrier in any person's own self-perceptions, things we accept as true and unyielding but never actually think about. It's part of being human: we can't think about everything without going bughouse nuts, so there are many things we just don't think about, and some of those we really
should think about. When a woman takes a serious, sensitive, considered look at a male character, with the aim of giving that character a fair and honest portrayal, I think she will often times bring out those sorts of unconsidered assumptions into the light where they can be looked at freshly. Again, I assume that this is likely the case for the reverse circumstance. That sort of examination can be very good for those who want to understand
themselves better.
Case in point, when I was reading
Goblet of Fire and
Order of the Phoenix I was very bothered by Harry's seething, unthinking anger, and the stupid, self-destructive ways he dealt with others because of his anger. I finally spent some thought on why it bothered me so much, and realized that it was because it was so very like the anger I felt myself at that age, and that I could see how, out of that anger, he was doing things that he would regret later. Added to that, from the perspective of having lived through those years myself (and quite a few more besides), I
also could see just how trivial many of the things he was angry about really were, while at the same time remembering all too clearly how vital they would
feel from the inside.