What do conference organizers expect from an invited speaker?
Here's my take: as a plenary speaker, you will have an audience that is broader than those who may come to a minisymposium or parallel session, and consequently also have a less deep understanding of technical details of your particular field of work. They may also lack an understanding of the motivation for what you are doing: For things in my particular field, I know why people want to do them, but for other areas I often would like to know "why should I care" before I want to hear the details.

Consequently, the talks that I have often found to be a bit boring are those that really are just longer minisymposium talks. The ones I find interesting are those that explain to me the bigger context of a problem: where does it come from, what are the historical connections, were there dead ends in developing solutions, etc. Then show me how you approach the problem and where this leads. I also find it interesting to hear about open problems and ideas for future research -- an invited talk should not just be about the great results of the speaker, but also inspire others to work in this field.