My experience is that in professional contexts, people come in expecting you to be great, which is a huge advantage if you act confident and secure. It feels like when someone says they're nervous, or, in a church meeting, mumble something about how they wanted to say no to the bishop because they hate giving talks, that it undermines the strong position that a speaker otherwise starts with.

But maybe it depends on the kind of speaking. I speak several times a year at conferences, usually for smaller groups of 20-40, but occasionally in front of several hundred people, and these are all people who have paid a good deal of money to attend the event. Nobody there is compelled by work and they've often traveled from a distance to hear me and others talk about something that is very important to them. They come in expecting me to be great, and it's a subject that I know very well and at this point could just wing it and nobody would know. Over time, I've just grown in confidence, and really enjoy public speaking.