Although I really have no experience with most of it (no children, commuted in heavy traffic through my teens and early 20s and had no car, so couldn't afford to be afraid), what everyone else has said rings true intellectually to me, except for the thing about size being a disadvantage.
I can't TELL you how many men behind me in a paceline have grumbled about my size!
And vice versa, it's super easy for 5'3" me to tuck in and hang on with a much stronger group. They don't even mind so much if I only take token pulls, since I'm basically not doing anyone any good at the point anyhow. 
As far as hills, that extra 20-30# of body weight that a man has to drag up a hill costs him WAY more than the extra 2-3# if the woman can't afford a bike as snazzy as his. BTDT, with men who can completely dust me on the flats.
Last edited by OakLeaf; 05-12-2012 at 06:23 AM.
Speed comes from what you put behind you. - Judi Ketteler