On the negative side… while it’s great for the speaker, for all the reasons you cite, the idea that everyone should “get up there” makes me wince slightly. If I’ve paid to hear people speak I want to hear people who are really, really good at what they do, or really know a lot more than most people about their subject. From an audience-member’s point of view I don’t want lots of people going to speak at things just because they want to. This is why I rarely speak at things - because I assume there are plenty of people who know more than me about almost everything I know something about.
One other point: “It’s still true that a woman in a mixed group is often doing well if she manages to finish a sentence without people talking over her.” I obviously can’t speak for women, and I don’t know how it compares for women vs men, but this isn’t only a problem for women. It drives me nuts when people interrupt me or talk over me. Just getting a word in often requires a more agressive conversational style than I have.
But otherwise, yes, speaking is, as you say, worth doing and seems to give you more authority (and fun, and nerves) than, say, many lengthy blog posts would.