I tend to agree, and try to put in practice, the idea of practicing with my partner is above all based on their and mine combined abilities. Regardless of gender. That being said, I have noticed that the newer average female student seem to pick up a little quicker than the average male student. I have said openly in class that women do better in aikido than men, maybe because they have a lower center and rely on technique more than men. I just had shiho-nage done on my sorry ass by a brand-new female student, and my wrist still smarts; I love it!
And as far as what Cas mentioned about "I have come across SOME men who have either thrown women in a very soft, flippant way, or harder than the men, both maybe suggesting that they would prefer to train with men only.", those students ('cuz were all students) are for the most part not at peace with themselves and are fighting with what aikido is trying to teach them; love.
Great string Cas.