You know, as someone who has taken his fair share of anthropology (and women's anthropology, at that!), I have to say that the idea of "women are weaker but wiser/more charismatic" is just silly.
This trait is something that is culturally stressed, not truly biological. While most cultures have a bias towards male dominance in some ways, not all cultures assume males will be stronger. In some north african cultures, women are stronger, because they are responsible for grinding millet (which builds upper body strength), while the men are more dextrous from the hunting that they traditionally perform.
Not to mention that, historically, women carried children quite frequently, and probably had more endurance in some ways. And probably still do.
Margaret Mead was surprised to find polynesian cultures in which the men perfumed themselves and wore flowers, worrying about their hair - and this was "manly" behaviour. It's really all cultural.
All of these things that we relate as being "biological" are really responses to cultural stresses. Women are seen as more caring as a result of the cultural responsibility of motherhood - it's not hard-wired into their brains (or, at least, not as much as you'd think).
I'll be dead honest, here. I'm stronger than my girlfriend, but not by much. And I know plenty of women that could kick the crap out of me. A +2 strength modifier is a big deal - and it's far too big a deal to replicate the differences between the genders.
So, yeah, I find the idea of seperate stat modifiers slightly offensive. I think it's going too far for the sake of a game, and if I saw it in the Character Generation section, I'd probably overrule it, or even stop playing.
Now, rules that stress cultural gender roles are AWESOME in my book - by all means, have Viking Shieldmaidens and have a rule that only men can be legionnaires (provided that women have a "girls-only" group that's worth joining, too). That's just great campaign flavour. But a rule that says "Well, women are naturally weaker, and I'm going to enforce that with a huge penalty" is just silly - and it smacks dab of sexism.
Again, it's just My two cents.