Stating your credentials - yay or nay?

I've heard some speakers say that it's important to establish your credentials at the beginning of a presentation, so your audience knows that you're a credible expert.

I say, fuhgeddaboudit. You've already been invited. You have obviously established your credentials with whoever organized the speaking engagement.

What the audience wants to know is what's in it for them? What are the benefits you're going to give them in exchange for their valuable time? What practical, useful, relevant information are you going to send home with them?

Put your bio into a handout and use your opening to engage your audience, to grab their attention and let them know you're there to serve them. Sometimes you're lucky enough to have someone to introduce you, but if not, don't waste your audience's time talking about yourself.

Rambling on about your background, education and vast experience will send your audience immediately to snoozeland and it will be harder to get back the attention you've already lost.