Actually, rather than Jamie striking me as not behaving as a man might be expected, it was Claire who seemed to me to be the one who was not acting in a traditional gender role. Most specifically, it was the way she seemingly had no qualms about bedding Jamie for her own purposes that struck me as something a man would be more likely to do. Of course, the fact that she was quite the warrior by the book's end did nothing to lessen that impression. But overall, despite Claire's relatively easy acceptance of the necessity to sometimes solve her problems with a knife, I had no real trouble with the gender roles of either of them.
I will say I didn't understand their mutual enjoyment of pain during sex. Maybe I've just been doing it wrong, but it seemed a tad perverse. Oh, well. Different strokes as they say....