Great post, this is so true. We pay a lot of attention to the release emails we make. They are important documents that that explain the value proposition of the app.
We often select 3 items and spotlight them in order of priority. So there is also an element of selecting what has the biggest impact on the user, because most people will not read it all. If they will only remember one thing, what is the one you want them to take away?
And as you said, often the spotlights are things that took just a few hours while the work that took the most efforts appears a small bullet point in the bottom.