I've come to similar conclusions. Salary discrepancy is another related phenomenon. My observations are completely based on anecdotal evidence, but having had to interview people for jobs, I'm also now of the opinion that women are paid less than men because they ask for less money. In general men asked for more money than we, as potential employers, had anticipated. Women asked for less money. The difference was significant, at about 10% of the salary (e.g., on a $50K position, men might ask for $55K and women might ask for $45K).
Once I started seeing this pattern, I met a girl who was looking for her first programming job out of school. I insisted she ask for a salary figure that I would have asked for in her position. She was extremely hesitant. She ended up asking for $5K under what I suggested, but when the interviewer didn't balk, and in fact gave her $3K more than she had requested, she was ecstatic. She phoned me up in complete disbelief.
On the other hand, I have another friend who's very unhappy in her programming job right now because she asked for so little money to start and now she just gets cost-of-living raises, which themselves have been frozen due to the current state of her company's finances. She knows that men make $15K to $20K more than her doing the same job, and I keep trying to coax her to ask for a big raise anyway, so it's at least on her boss' radar. I'm actually meeting with her in a couple of hours for a little developer meet and greet, so I'll be sure to remind her again :)
The issue of sexism is a delicate one because it involves perceptions. Also, most men today try not to be sexist. Watch an episode of Mad Men and you'll see how far the workplace has come. What sexism is left is unintentional, subtle, and sometimes the result of both actions on the part of men and women in the workplace. If we want to come to a solution on sexism, I think we need to stop thinking of it as something that people do to other people, and start thinking of it as a phenomenon. People are more willing to discuss why something is the way it is rather than feel obligated to defend or otherwise justify their own actions.