Agreed! As I wrote to a comment elsewhere on this page: "Most of the time, they selected your talk based on their interest in the contents (and less so on your delivery), and so they want to learn a thing or two. They will be graceful towards your presentation (style, delivery, slides) if at the end they got what they came for: you sharing data, knowledge, insights or wisdom. You don't want [to make] that too difficult for them, so you should work hard on improving your presentation delivery, but sharing knowledge is appreciated over sharing jokes or just well-designed slides."